Final Reportof
IPhO2023
The 53rd International Physics Olympiad(IPhO2023)
Tokyo, Japan (July 10-17, 2023)

January,17, 2024

The IPhO2023 Organizing Committee
and
The IPhO2023 Association

Foreword
This is the final report of the 53rd International Physics Olympiad (IPhO2023) heldfrom July 10th(Mon) to 17th(Mon) 2023 at the National Olympics Memorial Youth
Center in Tokyo, Japan.
IPhO2023 was the first on-site execution of IPhO in four years since the outbreakof COVID-19 pandemic in 2020. It was the utmost pleasure for us, the organizers, tohave been able to welcome the delegations from around the world and to provide aface-to-face communication environment. We hope that each one of the contestantsbrought home happy memory that will further motivate his/her pursuit of future career.
At the same time, we hope that we were able to add a new page to the long successful
history of the International Physics Olympiad and has contributed something to thepromotion of science education in the countries/regions that participated in IPhO2023.
We would like to express our sincere gratitude to MEXT and Co-Organizers andSupporters listed in this report for their generous support and contributions that madeIPhO2023 possible.

KOBAYASHI Makoto
Chair, Organizing Committee of the 53rd International
Physics Olympiad (IPhO2023)
Honorary Professor Emeritus, High Energy Accelerator
Research Organization (KEK)2008 Nobel Laureate in Physics

CONTENTS
Foreword
1. Executive Summary
2. Chronology -- Long and Winding Road to IPhO2023*

page
1
3

2.1 Pre-History (before 2015)
2.2 Early Planning Period (2015 to 2019)
2.3 Outbreak of COVID-19 and Postponement of IPhO2020 (2020)
2.4 Period of Accelerated Preparations (2021 to 2022)
2.4.1 Fund-raising campaign
2.4.2 Logistics and social event planning
2.4.3 Design and production of experimental kits
2.4.4 Preparation for exam environment
2.4.5 Scientific calculator
2.4.6 Logo, conference goods, medals and trophies
2.4.7 Promotion of gender diversity
2.5 Count-Down Months (Jan to July 2023)
2.5.1 First circular and pre-registration
2.5.2 On-site or on-line: COVID-19 and other risks
2.5.3 Second circular and team registration
2.5.4 Assistance of visa acquisition
2.5.5 Recruitment of student supporters
2.5.6 Dry run of exam execution
2.6 IPhO2023 Period (July 8 to 18, 2023)
2.6.1 Last-minute rehearsal of exam execution
2.6.2 Arrival and registration of delegations
2.6.3 Opening of IPhO2023
2.6.4 COVID-19 situation during IPhO2023
2.6.5 Other issues and their counter-measures
2.6.6 Time table for students
2.6.7 Time table for leaders and observers
2.6.8 Ceremony programs
2.6.9 Closing of IPhO2023
2.7 Post-Event Works
2.7.1 Distribution of the experimental kits
2.7.2 Questionnaire survey

3. Preparation and Implementation of IPhO2023 Examination**
3.1 Composition of the Academic Committee
3.2 Academic Timelines
3.3 Making of IPhO2023 Exam Problems
3.3.1 Preparatory phase
3.3.2 Quality control of exam questions
3.3.3 Mass production of experimental equipment
3.3.4 Recruiting the markers
3.3.5 Rehearsals
3.4 Other Preparatory Tasks
3.4.1 Choosing the venues
3.4.2 Exam booths
3.4.3 Student codes and booth codes
3.4.4 Exam tools
3.4.5 Designing the IT infrastructure
3.5 International Board Meeting (IBM)3.5.1 Discussion and decision of exam questions18

3.5.2 Marking and medal thresholds
3.5.3 Moderation
3.5.4 Medal decision
3.6 Conducting Exams
3.6.1 Printing works at IIS venue
3.6.2 Test administration work at NYC venue
3.6.3 Scanning and copying work at IIS venue
3.6.4 Marking

4. IPhO2023 Website, Circulars and Registration Forms*

35

4.1 IPhO2023 Website
4.2 Pre-Announcement
4.3 First Circular and Pre-Registration
4.3.1 First circular
4.3.2 Pre-registration form
4.4 Second Circular and Team Registration
4.4.1 Second circular
4.4.2 Photography consent form and commitment form
4.4.3 Flow chart of the team registration form
4.4.4 Team registration form
4.5 Third Circular
4.6 Request form of invitation letter for visa application

5. IPhO2023 Contest Results*

68

5.1 Participating Countries and Regions
5.2 Participants (contestants, leaders, observers and guests)
5.3 Contest results and awards
5.3.1 Medals and honorable mentions
5.3.2 Special prizes
5.3.3 Diversity commendation
5.3.4 Statistics of the contest results (score distribution)**

6. Organization and Logistics of IPhO2023*

78

6.1 Organization of IPhO2023
6.1.1 Organization chart
6.1.2 IPhO2023 Local organizing committee
6.1.3 Organizing committee and board members
6.1.4 Academic committee
6.1.5 Executive committee
6.1.6 Event planning subcommittee (Excursion/cultural event team)
6.1.7 Public relations subcommittee (Newsletter team)
6.1.8 Official photographers
6.2 Co-Organizers and Supporters
6.2.1 Co-organizers
6.2.2 Special supporters
6.2.3 Supporters and donors
6.3 Logistics of IPhO2023
6.3.1 Venue of IPhO2023
6.3.2 Social activities – Excursions (Event planning subcommittee)
6.3.3 Social activities – Japanese cultural experience
6.3.4 Social activities – Science an technology experience corner
6.4 IPhO2023 Handbook
6.5 IPhO2023 Newsletters

7. Feedback from Participants*
7.1 Feedback from Contestants on the Implementation of Examination
7.1.1 On the experimental exam108

7.1.2 On the theoretical exam
7.1.3 On the exam environment and operation
7.2 Feedback from Leaders and Observers on the Implementation of Examination
7.2.1 On the experimental exam
7.2.2 On the theoretical exam
7.2.3 On the International Board Meeting: environment and operation
7.3 On the Cultural and Social Events
7.3.1 Special lectures by Nobel laureates
7.3.2 Science and technology exhibitions
7.3.3 Cultural experience events
7.3.4 Stage performances
7.4 On the Overall Operation and Hospitality

8. IPhO2023 in Photos

127

8.1 Opening ceremony
8.2 Setting up the exam venue
8.3 International board meeting
8.4 Examination
8.5 Excursions (half day, metropolitan area)
8.6 Cultural events
8.7 Science and technology experience corner
8.8 Excursions (full day, Kanto area)
8.9 Special lectures by Nobel laureates
8.10 Final international board meeting
8.11 Closing ceremony
8.12 Farewell lunch

Afterword*153* drafted by IYE Yasuhiro** drafted by HAYANO Ryugo

Appendix 1
Examination problems and solutions
Experimental examination
General Instructions
G0
Question 1
Q1
Answer 1
A1
Question 2
Q2
Answer 2
A2
Theoretical examination
General Instructions
G0
Question 1
Q1
Answer 1
A1
Question 2
Q2
Answer 2
A2
Question 3
Q3
Answer 3
A3
Appendix 2
Brochure of Cultural Experience Events
Brochure of Excursions
Appendix 3
Newsletters Issues 1 to 10

1. Executive Summary
The 53rd International Physics Olympiad (IPhO2023), Tokyo, Japan
July 10th to 17th, 2023
The National Olympics Memorial Youth Center (NYC)
Kamizono-cho, Yoyogi, Shibuya-ku, Tokyo
Nippon Seinenkan Hotel (NSH)
Kasumigaoka-cho, Shinjuku-ku, Tokyo
The Institute for Industrial Science (IIS), The University of Tokyo
Komaba, Meguro-ku, Tokyo[Date][Venues][Attendance]
Participating Countries and Regions
Regular Participation
Team of Individuals
Observer Countries
Guest Team

80
1
2
1

Participants (Figures in parentheses are number of females.)Contestants (Students)
Regular Contestants
388 (43)
Guest Students
4 (1)Sub Total
392 (44)
Adult Participants
Leaders
Observers
GuestsSub Total
Total number of participants

155 (13)96 (19)17 (9)
268 (41)660 (85)[Awards]
Medals and Honorable Mentions
numbercumulative
Gold medals
37
37
Silver medals
74
111
Bronze medals
103
204
Honorable Mentions
54
258
Regular Contestants
388
Special Prizes
Absolute Winner
1
Best Performance in the Experimental Examination 1
Best Performance in the Theoretical Examination
2
Diversity Commendation (given to teams)

ratio
9.5%
28.6%
52.6%
66.5%
100%

4 teams[Organizing Side]
Organizers
The Organizing Committee of the International Physics Olympiad 2023
andThe International Physics Olympiad 2023 Association
with the support of the Ministry of Education, Culture, Sports, Science and Technology(MEXT), Japan

1

Co-Organizers
Academic Societies
Government Affiliated Organizations
Universities

4
5
6

Number of Persons Involved
A. Organizing Committee
A-1 Organizing Committee Members
36
B. Academic Committee
B-1 Academic Committee Members
19 [4 of which are included in A-1]
B-2 IT Technical Staff
5
B-3 Moderators (assistant profs, postdocs) 23
B-4 Markers (graduate students)
23
B-5 Invigilation
70 [21 of which overlap with C-3]
B-6 Exam printing, Answer scanning20
B-7 Answer numerical input (Excel sheet) 27
Subtotal
187 [minus 25 for the grand total]
C. Executive Committee
C-1 Executive Committee Members
4 [3 of which are included in A-1]
C-2 Student Leaders (events, newsletters) 14
C-3 Student Supporters (team attend)
142
C-4 Exam Partition Designers
2
C-5 Photographers2
C-6 Nurses
2
Subtotal
165 [minus 3 for the grand total]
D. IPhO2023 Association (Secretariat)
D-1 Administrative Staff
8
Grand Total

369*Personnel and temporary staff of the official travel agency (Tobu Top-Tours) are not includedin this count.
**Of the 369 persons counted above, about 20 persons, including the chairs of the committees,
the head of the subcommittees, the exam preparers, the staff of the secretariat and theauditors, made long-term (more than 5 years) commitment from the early planning stage.
Additional 30 persons joined the organizing body for the last two to one years for the actual
planning of the programs, including cultural events, excursions etc. The rest were recruited tovarious roles for the operation of IPhO2023 during its period.

[Supporters]
Special Supporters
Diamond Supporter Companies
Sapphire Supporter Companies
Ruby Supporter Companies
Supporters
Supporting Members (companies and groups)
Supporting Members (individuals)
Donors (companies and groups)
Donors (individuals)

8
18
22
13
18
63
112

[Web sites]
https://international-physics-olympiad2023-tokyo.jp/ International page in English
https://international-physics-olympiad2023.jp/

Domestic page in Japanese22. Chronology --- Long and Winding Road to IPhO2023
2.1 Pre-History (before 2015)
The International Physics Olympiad (IPhO) first held in Warsaw (Poland) in 1967, has developed to aworld-wide competition of young talents in the field of physics. IPhO has been held every year (with a few
exceptions) by host countries taking turns. In the long history of IPhO, Japan joined the IPhO community
relatively recently. Japan sent its first delegation to IPhO2006 in Singapore and participated regularly eversince. An organization by the name of “the Committee of Japan Physics Olympiad (JPhO)” is the body
responsible for domestic selection and dispatch of the representative contestants to each year’s IPhO.
The IPhO Statutes and Regulations state that “each country should, within five years of entry, declare its
intention to host a future Olympiad”. The JPhO delegation leaders to IPhO2009 in Mexico conveyed
Japan’s intention to take the responsibility of hosting IPhO but no earlier than a decade from then, possibly
around 2023, to the President of IPhO at that time. Soon after, JPhO was approached by the IPhO
President for the possibility of hosting IPhO in 2022, and accepted the request. Thus, the preliminary
setting for an IPhO in Japan was set with the target year 2022, and Japan became listed as prospective
host country in the timeline on an unofficial webpage of Physics Olympiad.

2.2 Early Planning Period (2015 to 2019)
The substantive activity as a future host country began in 2015 with KOBAYASHI Makoto‘s acceptanceof chairmanship. On May, 2016, the kick-off meeting of the IPhO2022 Organizing Committee was held by
the core members. Three committees --- the Executive Committee (chaired by IYE Yasuhiro), theAcademic Committee (chaired by HAYANO Ryugo) and the Fund-raising Committee (chaired by SAKAKI
Hiroyuki) --- were formed. In consideration of potential conflict of interests, it was determined from theoutset that the organizing body of IPhO2022 should be appropriately demarcated from JPhO which was
the organization conducting domestic selection and dispatch of the contestants, especially with regard to
the exam problems creation.
The Initial tasks of the IPhO2022 Organizing Committee included the followings:(1) To communicate with the Ministry of Education Culture Sports Science and Technology (MEXT),and the Japan Science and Technology Agency (JST -- a funding agency under the jurisdiction of
MEXT) for the governmental support of hosting IPhO2022.
(2) To communicate with physics-related academic societies, including the Physical Society of Japan,
the Japan Society for Applied Physics, and the Physics Education Society of Japan.
(3) To contact with the Tokyo University of Science for installation of the IPhO2022 Secretariat officewithin the campus.
(4) To conduct survey of facilities which are both suitable as the venue of IPhO in Tokyo and areaffordable.
(5) To estimate the overall cost of hosting an IPhO and make up plans for fund raising.
(6) To recruit sufficient number of able physicists who are willing to work together anonymously tocreate and brush up the exam problems.
We contacted the Human Resources Policy Division, the Science and Technology Policy Bureau of MEXT
early on, so that the MEXT will officially endorse the invitation of IPhO to Japan when the appropriate timecomes. We were told that the subsidy from MEXT would be at most the amount equal to the funds collectedby the organizing body. The total cost of hosting an IPhO in Tokyo was roughly estimated as 400 million
JPY (depending largely on the accommodation cost and on the extent of outsourcing logistics), by
reference to the publicly disclosed account settlements of other Science Olympiads of comparable size
(biology, chemistry etc.) held recently in Japan. This meant that we would have to secure about 200 million
JPY as self-help revenue. The total amount of participation fees paid by the delegations from various
countries/regions was estimated to be about 50 million JPY. Thus, the fund-raising target was set at 150

3

million JPY, which seemed quite a challenge in view of the somewhat recessing economy in Japan at thattime.
In regard to the selection of IPhO venue within the Tokyo metropolitan area, the National Olympics
Memorial Youth Center (NYC) seemed to be the only practical choice, so that we placed a tentative
reservation for the period of July 10-18, 2022. (The official reservation had to wait until one year prior to
the actual event.)Three physics-related academic societies, the Physical Society of Japan, the Japan Society for Applied
Physics, and the Physics Education Society of Japan, agreed to be co-organizers. Later, the BiophysicalSociety of Japan joined.
In April 2018, a General Incorporated Association entitled “International Physics Olympiad 2022
Association (IPhO2022 Association)” was established with KOBAYASHI Makoto as the president, and heand IYE Yasuhiro assuming the positions of representative director for legal registration. This Association
was the implementation body of IPhO2022 and the recipient of the government subsidy. The office of the
IPhO2022 Association was set up within the premise of the Tokyo University of Science, which agreed to
be one of the co-organizers of IPhO2022. SUZUKI Akifumi, a former MEXT officer, was recruited for theadministrative office head. Thus, the IPhO2022 Association took its initial shape.
Neither HAYANO nor IYE had prior experience of attending IPhOs. HAYANO paid visit to IPhO2016 in
Switzerland/Lichtenstein, and IYE attended IPhO2017 in Indonesia and IPhO2019 in Israel to getfamiliarized with the International Board Meeting and other matters relevant to running an IPhO.
The Academic Committee of IPhO2022 chaired by HAYANO Ryugo made an early start. He managed torecruit physics professors and formed two subcommittees for experimental and theoretical problems. They
held regular meetings, initially starting with review of the exam problems of the past IPhOs. The members
and activities of the Academic Committee were kept undisclosed until the completion of the real
examination. The detailed account of the Academic Committee’s activity is given by HAYANO, in Chapter
3 of this report.

2.3 Outbreak of COVID-19 and Postponement of IPhO2020 (2020)
Things completely changed in early 2020 when COVID-19 pandemic started to spread like a wildfire allover the world. IPhO2020 scheduled to be held in Lithuania that year was forced to be postponed to thenext year. We were approached by the IPhO President and were asked if the IPhO2022 in Japan could beshifted to 2023. Given the unprecedented circumstances, we agreed, after consulting with MEXT, on therescheduling. Accordingly, the Association was renamed IPhO2023 Association, and other relevantchanges were made.
In July 2021, with the global situation of COVID-19 aggravated, the Lithuanian organizers had no otherchoice but to hold IPhO2021 on-line, for the first time in the IPhO history. The Lithuanian organizers
requested each participating country to appoint invigilators who were not the members of the dispatchingorganization (in the case of Japan, JPhO, mentioned earlier). In response, HAYANO and IYE served as
invigilators of the exam executed on-line. This offered us a good opportunity for us to recognize various
issues with regard to on-line style competition, thus get prepared with an unwanted turn of event thatsimilar situations occur in 2023. While we wanted to make IPhO2023 an on-site face-to-face event by allmeans, we also had to keep in mind an alternative scenario of on-line execution of IPhO2023. The
necessity of such “two-way planning” was very stressful throughout the preparation of IPhO2023. We did
not consider an option of so-called “hybrid style” implementation, because that would make it extremely
difficult to secure equal conditions and fairness in the contest.

2.4 Period of Accelerated Preparations (2021 to March 2023)
2.4.1 Fund-raising campaign

4

In 2021 and 2022, we accelerated our fund-raising effort. Three categories of “Special Supporters” titles(Diamond, Sapphire and Ruby) were installed according to the level of contributions. Calls for donations
from individuals, groups and companies, irrespective of the amount of money, were continued. In
retrospect, we were fortunate to be able to achieve more or less the initially set fund-raising target of 150
million JPY by March 2023.
2.4.2 Logistics and social event planning
In 2021, about two years before the actual IPhO2023 event, we selected Tobu Top Tours company as theofficial travel agency of IPhO2023, after an appropriate process of bidding. Tobu Top Tours formed a
special team for IPhO2023 and handled various aspects of logistics in close collaboration with the
IPhO2023 Secretariat. The work included reservation of rooms in the NYC and the Nippon Seinenkan
Hotel (NSH), assistance of visa applications, arrangement for airport pickup and transportation during
IPhO2023, and many others.
As for the planning of social events such as excursions, cultural experience sessions, we wanted toincorporate senses and preferences of youngsters as much as possible. For this purpose, we recruited
students of Tokyo University of Foreign Studies and International Christian University and appointed themas Student Support Leaders. They formed a team with YAMASHITA Minoru, Head of the Event Planning
Subcommittee. Over the last one and half years, the team held regular meetings and put forward ideas for
cultural experience events, which were materialized in the style of “en-nichi” (festival held at temples or
shrines on designated religious days) with many stalls providing foods and games and “bon-odori” (group
dance at summer festival). As for the excursions, they actually took the trouble of visiting each of thecandidate destinations and checked all the relevant issues, including trip route and time, where to visit andtake lunch etc. In this way, they made plans of four half-day courses and four full-day excursion courses,
and they produced brochures which are reproduced in the Appendix 2. Each team of students could
choose 2 half-day excursion courses out of 4 for Wednesday and Friday and 2 full-day excursion courses
out of 4 for Saturday and Sunday. The adult participants (leaders, observers and guests) were offered 2
half-day excursions in the time slots when students engaged themselves in the exams on Tuesday andThursday.
2.4.3 Design and production of experimental kits
The Academic Committee narrowed down the candidates of exam problems by spring of 2022. The big
issue was to design and materialize the experimental apparatuses. The Academic Committee approacheda few companies capable of producing them. Going through the calling for bids, Shimadzu Rika company
was selected. Shimazu Rika and the Organizing Committee entered into a contract for the production of
the experimental kits with an appropriate non-disclosure agreement. A few rounds of trial production andoperation check were made before proceeding to the final production of 500 sets.
Here, it is worthwhile to put on a record, a specific problem we encountered in connection with thepossibility of remote execution of the exam. If the exam were to be conducted remotely, the experimental
kits would have to be shiped to the participating countries in advance. Time and trouble of custom
clearance in different countries were well anticipated. What came to our attention in later stage was the
RoHS (Restriction of Hazardous Substances) Directive in European countries. It turned out that theexperimental kits being developed contained some materials such as lead-containing solder, brass withtrace amount of cadmium, and metal parts surface-plated with hexavalent chromium, which may notcomply with the RoHS regulations in EU, although they are perfectly okay within Japan. After discussions
with Shimadzu Rika Company, the specs of the relevant parts were changed (with extra costs) just to beon the safe side, and the parts in question were replaced by those made of materials complying with RoHS.
Although this measure turned out to be unnecessary because the contest was held on-site, this should be
put as a note for future IPhOs.

5

2.4.4 Preparation for exam environment
Two gymnastic halls in the Sports Building of NYC were chosen as the venue of examination. Based on
the number of Pre-Registration Forms, we estimated the maximum number of contestants could be aslarge as 450. Planning of the layout of booths for individual contestants was made by HAYANO, Chair of
the Academic Committee. In addition to those two halls, a few additional rooms were reserved as extra
venue of examination, in consideration of possibilities such that some of the contestants should be
separated (e.g. due to COVID-19 infection), or would require special treatment (e.g. for medical reasonetc.).
The design and layout of booths to be set up in the gymnastic halls of NYC were planned by HAYANO
with a great help of FUKUSHIMA Katsuya’s group at Tokyo City University specializing in architecturaldesign. With due considerations of ecology, the partitions were made with cardboards and were designed
to be easy to assemble and dismantle and be apt for re-usage and recycling. After IPhO2023, some setsof the used cardboard partitions were donated to Tokyo City University as a stock for potential use at
emergency evacuation sites in an event of natural disaster etc.
2.4.5 Scientific calculators
Another important issue was scientific calculators to be used by the contestants. In the past IPhOs, it wascustomary to allow the contestants to use their own calculators provided they meet the regulations. This
made it necessary to check the spec of the models, and to clear the memories of the calculators prior to
the exam. In IPhO2023, CASIO COMPUTER Co. Ltd. offered to provide a suitable model of scientificcalculator. Making all the contestants use the same model of calculator has a lot of advantages in termsof equality of exam conditions. On the other hand, making all of them appropriately familiarized with themodel prior to the exams was the challenge. Fortunately, CASIO offered a web-based emulator programthat allowed prospective users to get used to the usage of the model. We provided the access codes tothe emulator program to each participating teams so that the contestants could get used to the usage ofthe calculator. In addition, we installed a special practice session on the first day of IPhO2023. Despite ourconcerns, it turned out that young students are so quick to get used to a new gadget. No complaints were
heard about the uniform use of the calculator provided by the organizer. We were impressed to find thatyoung students were “digital native” so that they were able to make use of the newly provided gadget
effortlessly (perhaps without even reading the manual) in a short period of time.
In this connection, it is our opinion that the part of the Regulations to Section 5 of the Statutes relevant tocalculators should be reconsidered: The Regulations state that “Contestants may bring into theexamination drawing instruments and approved calculators”. However, if, as practiced in IPhO2023, official
calculators are provided to all contestants and fairness is ensured by pre-training opportunity etc., then theprovision “permission to bring one’s own calculator” should be unnecessary. The Regulations also statethat “A calculator shall be an approved calculator if it is not a graphical calculator, its display has no morethan three lines, and if its user memory is completely cleared immediately prior to each examination.” Thispart of the Regulations seems outdated, given that new models of calculators are continually introducedin the market.
2.4.6 Logo, conference goods, medals and trophies
The logo of IPhO2023 was designed by Ms NAKANURA Maiko.
The “I” of the IPhO2023 logo is an exclamation mark representing
excitement of doing physics.
The “P” is a question mark symbolizing intellectual curiosity which is adriving force of research.
The “h” may be seen as the Planck constant, one of the fundamental
constants of physics (admittedly a strained interpretation).
The “O” is designed as a light bulb, a classic symbol of an “Eureka”
moment6

The IPhO2023 goods were (1)T-shirt, (2)cap, (3)bag, and (4)thermos bottle. Students were given all
four items, while the leaders and observers were given a T-shirt and a bag.

IPhO2023 T-shirts

IPho2023 Bag

IPhO2023 Caps

Thermos bottle

The design of medals to be awarded to the contestants who marked high scores carried the image of Mt. Fuji.
Mount Fuji is an undisputed symbol of Japan, and has been an inexhaustible spring of artistic inspiration. The
medals of IPhO2023 adopt one of the most famous images of Mt. Fuji taken from a series of masterwork wood
prints “Fugaku Sanju-rokkei (36 views of Mount Fuji)” by KATSUSHIKA Hokusai (1760-1849), renowned artistof Edo era, days of TOKUGAWA Shogunate lasted from mid 17th century to mid 19th century.

Wood print work “Gaifu-Kaisei(fine breezy day)”, also known
as “Aka-Fuji (red Fuji)” by
KATSUSHIKA Hokusai.

In the Statutes of IPhO, it is stipulated that gold, silver, bronze medals and honorable mentions are to beawarded to the contestants according to their exam achievements and that on top of these regular awards,
the host organization can award special prizes to the contestants who rank highest in the experimental
exam, highest in the theoretical exam, and highest in the total score. Following the practice of past IPhOs,
we prepared trophies for these top performers. To our surprise, two contestants tied at the full mark in thetheoretical exam. Given this unanticipated outcome, we hurriedly produced an additional piece of trophyand sent it to one of the two students about two weeks after the closing of IPhO2023.
2.4.7 Promotion of gender diversity

7

It had been adopted at the IBM of IPhO2022 (Switzerland, on-line) that a statement “Each country is
encouraged to promote gender diversity within its team” be added to the Regulations to the Sec. 3 of the
IPhO Statutes. In some of the past IPhOs, a special prize was awarded to the female best performer. We
deliberated on this issue and sought opinions of various people (men and women, senior and young) about
the idea of “best female performer prize”. Although opinions varied among seniors, young female students
unanimously opposed the idea. Their shared opinion was that such a prize would be insulting to female
contestants who would like to compete on the same ground regardless of gender. After taking account ofvarious opinions, we decided not to award a “best female performer prize” in IPhO2023. Instead, we
decided to give “Diversity Commendation” to those teams representing well-balanced gender mixture andachieving respectable results in the contest.
In connection with the gender issue, we comment that we made the gender entry of the Team Registration
as three choices consisting of “male”, “female”, and “decline to identify” in consideration of transgenderpersons. It turned out no one chose the third option this time, but this would be something to be paid
attention in organizing future IPhOs.

2.5 Count-Down Months (Jan to July 2023)
2.5.1 First circular and pre-registration
In late 2022, IPhO Secretary STANLEY provided us the list of leaders of countries/regions which
participated in at least one of the previous three IPhOs -- IPhO2019 (Israel), IPhO2021 (Lithuania, on-line)
and IPhO2022 (Switzerland, on-line) with their e-mail addresses. We sent an e-mail of pre-announcement
on Jan. 17, which was also intended as communication test.
On Jan. 24, we sent out the First Circular and simultaneously opened the Pre-Registration site in whicha Pre-Registration Form was to be filled out by a principal contact person of the prospective participating
country/region, so that we can collect tentative numbers of participants.
In addition to the countries/regions with the record of participation in the past, we were approached bysome twenty individuals. Half of them were high school students who wanted to participate without knowing
the rules of IPhO. We let them know that one has to go through the domestic selection and advised tocheck the relevant system in their respective countries/regions. The other half were physics teachers or
professors who wanted to send a team to IPhO for the first time. We referred to the IPhO Statutes andexplained them that it is a general practice that a country/region first entering IPhO should do so as anobserver country/region and has to pay the prescribed participation fee. After many exchanges of e-mails,
many of them dropped their idea or simply disappeared from communication. The countries eventuallyparticipated either as observer country or guest team were those listed in Sec. 5.1.
2.5.2 On-site or on-line: COVID-19 and other risks
Due to the COVID-19 pandemic, the 2020 competition was canceled, and both IPhO2021 (Lithuania) andIPhO2022 (Switzerland) were forced to be held remotely. We, the organizers of IPhO2023 had to prepare
for IPhO2023 in two ways. Namely, while we wanted to realize IPhO2023 as an on-site face-to-face event,
we had to consider the option of on-line implementation in parallel until a fairly late stage of preparation
Learning from the experience of exam invigilation for the remote implementation of IPhO2021 (Lithuania),
we knew that some countries could take a long time for customs clearance, so a final decision on theimplementation format (on-site or on-line) had to be made by the end of March at the latest. Fortunately,
the situation had calmed down considerably by early spring, so we decided to go ahead with on-site
implementation of IPhO2023 at the Organizing Committee Meeting on March 24, and immediately notified
the participating countries/regions by e-mails.
Starting from May 8th, Japanese government re-classified COVID-19 from Class 2 to Class 5,deregulating various infection prevention measures. Accordingly, we decided to leave mask wearing andother infection prevention measures to individual discretion during IPhO2023. On the other hand,8considering a possibility of infection development during IPhO2023, we included the following clause in
the Commitment Form to be signed by all participants:
I commit myself to cooperate with the IPhO2023 organizer for a safe execution of the event.
I obey the Japanese laws and the usage rules of the National Olympics Memorial Youth
Center. I follow directions of the IPhO2023 organizer with regards to the COVID-19 infection
prevention and emergency safety measures against natural disasters such as earthquake.
Preparations were made to stock masks, disinfectants, thermometers, antigen test kits, etc. at thecompetition headquarters in case infections spread during the competition period.
In the process of preparation for IPhO2023, we had identified the following risks and potential incidents
in addition to COVID-19 that should be kept in mind: (a) Natural disasters such as earthquakes andtyphoons, (b) Illness, injury, involvement into crimes or accidents, and disappearance of participants, (c)Troubles between participants due to international tensions. Fortunately, no troubles so serious to hinder
a safe operation of IPhO2023 occurred.
2.5.3 Second circular and team registration
The Second Circular was distributed on April 14, 2023 and the website for the team registration was
opened. The Google form for the team registration was quite large in volume, because we had to collect
all the relevant data including passport photocopies, face photos, agreement forms, commitment forms,
etc. Some teams whose internet environments were less than ideal experienced difficulty in uploading thelarge volume of data. We had to handle those cases individually.
The deadline for the team registration was set at May 15. However, many countries/regions could notmeet this deadline because they did not finalize their domestic selection. Many Asian countries waited theoutcome of the Asian Physics Olympiad held in late May. Such delay in finalizing the membership of theteams rippled to the delay in visa acquisition process and in finalizing the travel plan as stated below.
2.5.4 Assistance of visa acquisition
Depending on their nationalities, some participants were required to get visas for entry to Japan. In theFirst Circular, we recommended the leaders of such teams that include members in need of visas to act
well in advance for a visa application referring to the website of the Ministry of Foreign Affairs, Japan
https://www.mofa.go.jp/j_info/visit/visa/index.html. We offered that the Organizer would provide invitation
letters to assist with the visa application upon request and registration of relevant information.
However, some countries/regions could not take actions for visa application either because the selectionof the representative contestants was not finalized until June as mentioned above, or, simply the necessityof visas slipped their mind. Administrative procedures of visa issue differed from one embassy of Japan toanother. Late filing of visa application by some of the participating teams caused a lot of paper works intight schedule for the Organizer.
2.5.5 Recruitment of student supporters
We started recruitment of student supporters (part-time workers) who would help the operation of
IPhO2023 in various aspects; (a)attending the students during their stay and excursions, (b)assisting
implementation of the examinations, and (c)assisting implementation of cultural and scientific experience
events. The recruitment was extended to the Tokyo University of Foreign Studies (TUFS), The
International Christian University (ICU), Tokyo University of Science (TUS), Tokyo City University (TCU)
and Sophia University. The applicants were interviewed and were assigned the tasks according to theirskills and availability during the IPhO2023 period. Some of the former IPhO contestants, now university
students, also joined the supporting team.
In addition to the student supporters, we recruited cultural clubs of university students which would show
their performance as entertainment at the Opening and Closing Ceremonies and cultural events. A few
clubs took up the task: the wadaiko (Japanese drum) club of International Christian University, the Karate

9(Japanese martial arts) club of ICU, the Koto (Japanese harp) club of Sophia University, and the Sado (teaceremony) club of Tokyo University of Foreign Studies.
2.5.6 Dry run of exam execution
On May 13th (Sat.), the Academic Committee carried out a dry run of the examination execution. All 46
markers were assembled and asked to try solving the actual exam problems in the morning, (They had
signed the non-disclosure agreement.) Then, in the afternoon, they were trained to grade those answer
sheets. This dry run was quite meaningful in digging up potential problems of the marking process andgaining consensus on the scoring criteria.
It Is stipulated In the IPhO Regulations that the host organization should set an opportunity for an advancevisit by the IPhO President. We thought this dry run was a suitable opportunity for President RAWAT to
pay a pre-visit. Fortunately, he was able to accept our invitation and inspected the dry run. He got a briefingfrom the Academic Committee Chair HAYANO, and put his hand on the experimental kits, and inspected
the facilities of the venue of IPhO2023. President RAWAT expressed his satisfaction about the preparation
status of IPhO2023 both in terms of the contest implementation and all aspects of logistics.

2.6 IPhO2023 Period (July 8 to 18, 2023)
2.6.1 Last-minute rehearsal of exam execution
On July 8th and 9th, the installation of the exam environment and the last-minute rehearsal of exam
execution were carried out. The rehearsal included, (a)printing of the numerous pages of the exam
problems, the answer sheets, and the work sheets, (b)distributing, collecting and sorting of the exam
sheets, (c)transportation of the answer sheets and work sheets from the NYC to the marking center at theInstitute for Industrial Science (IIS) in Komaba II Campus of the University of Tokyo, and (d)scanning andconversion to PDF of those answer sheets and work sheets.
At NSH where the International Board Meeting was to be conducted, high capacity internet line wasinstalled by the special IT team on the 9th, the day before the first IBM.
2.6.2 Arrival and registration of delegations
We asked each delegation to enter the flight schedule in the Team Registration Form. However, because
many airlines had reduced the number of flights on account of COVID-19 pandemic, quite a few teams
apparently experienced difficulty in finding appropriate flights and could not fix their travel schedule until
the last minutes, which in turn caused difficulty on our side to make arrangement of airport pick-up service
and accommodation for the night of their arrival to Japan. We prepared a new Google Form to be filled out
by those teams as soon as their flight schedule were fixed.
Still, the majority of the participating teams entered Japan either at the Narita International Airport orTokyo International Airport (Haneda) on July 8th or 9th, were picked up by our travel agency and transported
to the venue of IPhO2023 by chartered buses.
Upon arrival to the NYC, each team was received at the registration desk, where the students were
greeted by a student supporter who was to escort them during IPhO2023. After picking up the IPhO2023
goods and handbook, students were then led to a drop-off desk where they were asked to hand over theirpersonal computers, smartphones, and any other electronic devices with communication function,
including bluetooth headphones etc. Those devices were returned to them after the completion of thetheoretical exam on July 13th (Thu).
A get-together party was held in the evening of 9th (Sun) at the reception hall of the International Exchange
Building of NYC. After the get-together party, the adult participants (leaders, observers and guests) weretransported to the NSH.
2.6.3 Opening of IPhO2023

10

The Opening Ceremony started at 10:00 on 10th (Mon) with the Opening Address by KOBAYASHI Makoto,
Chair of the Organization Committee. The Minister of Education, Culture, Sports, Science and Technology(MEXT), NAGAOKA Keiko, gave a welcome address. In connection to the attendance of the Minister, we
had been instructed by the MEXT to make the number of attendants in the auditorium minimal for the
security reasons. Accordingly, we decided to accommodate only the students in the main auditorium andthe adult participants were seated in a separate room where video coverage of the opening ceremony was
shown on a screen. Some voices of complaint were heard from adult participants, but we were not allowed
to reveal the reason for admission restriction, either. The Minister left the venue after her address, andthen each team of students were called to the stage.
After the formal part of the ceremony, “wadaiko (Japanese drum)” play by students of International
Christian University and “karate (Japanese martial arts)” demonstration by students of Sophia University
were performed on the stage.
Right after the Opening Ceremony, the leaders and observers were transported to NSH where the first
International Board Meeting was to be held from 14:00.
This summer of 2023, the International Mathematical Olympiad (IMO2023) was also held in Japan(Makuhari, Chiba) with the period of July 3rd to 12th partially overlapping with that of IPhO2023. We were
aware that among the IPhO2023 contestants, several students also participated in IMO2023 where theexams were to be completed by 9th (Sun). We instructed those students to come to the IPhO2023 venue
and drop off their communication devices at the latest by 14:00 on 10th (Mon), which was the time the IBM
started and the experimental exam problems were disclosed to the team leaders and observers. Some ofthose students wanted to attend the closing ceremony of IMO2023 on 12th (Wed), but we did not give them
permission to go out the NYC since it was the day between the experimental and the theoretical exams.
There was an incident that two students of a certain team missed their flight connection and arrived at
Narita Airport in the evening of 10th (Mon) when the first IBM session was already in progress. Since thesestudents had failed to hand over their communication devices by the designated time (14:00, the startingtime of the first IBM), we thought they should be disqualified as regular contestants but be only accepted
as guest contestants. However, there were no clearcut statements in Statutes and Regulations. Although
we eventually agreed to treat them as regular contestants following suggestions by IPhO President andSecretary, we felt that the rule should be clarified for such cases.
2.6.4 COVID-19 situation during IPhO2023
The first half of the IPhO2023 period went by without any serious incidents. But in the second half, someteam leaders developed symptoms of fever and tested positive for COVID-19. Antigen tests wereadministered for roommates and close contacts. It turned out that the test kits stocked in advance were
not sufficiently sensitive, so we visited nearby pharmacies to purchase more test kits. Roommates who
also tested positive remained in isolation, while those testing negative were moved to other rooms,
isolating only the infected individuals. Meals were delivered by hotel staff. The management of NSH wasvery cooperative and flexible, securing alternative rooms on short notice. In total, 5 team leaders tested
positive. Attitudes toward COVID varied by countries and individuals. In one case, we had to argue withan infected individual who strongly complained about being isolated in his hotel rooms (despite that he hadsigned the Commitment Form mentioned in 2.5.4).
Around this time, moderation sessions were scheduled, in which team leaders from each country/region
and Academic Committee members get together to discuss their respective marking results. In order to
conduct the moderation safely under the above situation, the number of participants was limited to 2 percountry/region. All the participants of the moderation session were required to have been proved negativeby antigen test and to wear masks throughout the session. Some 200 antigen test kits needed for thispurpose were hurriedly collected by visiting several pharmacies in the neighborhood of Nippon Seinenkan
Hotel (NSH).

11

Toward the end of the competition, infections also began appearing among students staying at the NYC.
With appropriate nursing care and medication, their symptoms did not go serious, and all teams were able
to depart on schedule.
2.6.5 Other issues and their counter-measures
The Handbook distributed to the participants included explanations of evacuation procedures in case ofearthquake/fire, and contact information in case of illness/injury, as countermeasures for natural disasters
and illnesses/accidents among participants.
Two nurses were stationed full-time during the competition period at the National Olympic Memorial Youth
Center (NYC). It was anticipated that some students might get sick after long travels and with mentalpressure for the contest. In the first half of the competition period, two students complained of disconfort,
but recovered after consultation by the nurses, drug prescription and rest in their rooms. They were tested
COVID negative.
With intense heat expected and actually continuing throughout the competition period, heat stroke
countermeasures included preparing ample mineral water, salt candies for electrolyte replenishment,cooling towels, etc., and urging students to stay hydrated through nursing staff and student supporters.
Care was taken to accommodate participants with medical conditions, disabilities, dietary restrictions(allergies, halal, kosher, vegetarian, etc.). The Team Registration Form included entry for notifying suchspecial requirements. Several dozen participants, both students and team leaders, required halal meals.
While basic accommodations were made in the dining hall, dissatisfaction was heard about the small
variety of halal menus. In particular, some restaurants could only provide vegetarian menus to halal diners,
forcing participants wanting to eat non-pork/non-alcohol meals to compromise.
Having heard of cases of visiting foreigners disappearing after entering Japan for international events,
invitation letters for visa applications were issued only after confirming the applicant’s affiliation, status,
passport copy, etc., with extra care taken for applications from countries with no prior participation record.
As for Russia and Belarus, we notified the contact persons at the time of Second Circular that “While wecannot invite the delegation as a national team, a team of individual contestants can be accepted”. As aconsequence, Belarus chose not to participate in IPhO2023 and Russia took the option of sending a teamof individuals. The Russian students were grouped as “Oly Team” and the accompanying adults werecategorized as observers without the right to vote at the IBM. The opportunity of moderation was
guaranteed.
Every participant was urged to pledge “no political activities or statements during the competition period”
by submitting a signed Commitment Form. As we took extra care of the Russian students throughout
IPhO2023, no particular troubles occurred, to the best of our knowledge.
Most of the contestants were minors requiring appropriate protection. Some countries seemed remiss intheir escort duties, allowing subsets of students to travel separately on different schedules without escorts.
There was a case that two students of a certain delegation missed the flight connection and traveled bythemselves to Narita Airport and had to be picked up upon their late arrival.
A student supporter was assigned to each team. Many of the student supporters were able tocommunicate with the contestants in language of their country/region. Their roles were to assist with thestay and to guide excursions. Contestants were instructed to act under the student supporters’ escort, butsome were spotted going out of the NYC on their own after dark. In a case that a contestant wished to goout of NYC, for example with a relative living in Tokyo, we granted it on condition that the person taking
out the student to submit a pledge document detailing the purpose and the time to be back at NYC.

12

2.6.6 Time table for students

IPhO2023 Student Program
July 9SundayJuly 10
MondayTime
13:00-17:00

Activity
Registration

17:00-19:00

Get Together

7:15-8:00
10:00-12:00
12:30-13:30

BreakfastOpening Ceremony
Lunch
Briefing on Calculators
Used for Examination
Free Time
DinnerCafeteria Fuji, Central Bldg. 2F
Large Hall, Arts Bldg. 1F
Cafeteria Fuji, Central Bldg. 2F

BreakfastEnter the Examination
Room
Examination (Experiment)
Lunch (light meal)

Cafeteria Fuji, Central Bldg. 2F

14:00-14:45
15:00-18:00
18:00-19:00
7:15-8:00
8:30

July 11
Tuesday

July 12
Wednesday

9:00-14:00
14:30-15:30
16:00-19:00

Cultural/ScientificExperience Events

18:00-19:00

Dinner

7:15-8:00
9:00-14:00

BreakfastHalf-day Tokyo Excursion 1

16:00-19:00

Cultural/ScientificExperience Events

18:00-19:00

Dinner

7:15-8:00

BreakfastEnter the Examination
Room
Examination (Theory)
Lunch (light meal)

8:30
July 13
Thursday

July 14
FridayJuly 15
Saturday9:00-14:00
14:30-15:30
16:00-19:00

Cultural/ScientificExperience Events

18:00-19:00

Dinner

7:15-8:00
9:00-14:00
16:00-17:40

BreakfastHalf-day Tokyo Excursion 2
Special Lectures

18:00-19:30

Dinner Party

7:15-8:00
8:00-19:00

Breakfast
Full-day Kanto Excursion 1

Place
Reception Hall,International Exchange Bldg. 1F

Large Hall, Arts Bldg. 1F
Cafeteria Fuji, Central Bldg. 2F

Athletic Bldg. 1F & B1F

Cultural events:
Reception Hall & Oka Tei,
Scientific events:
International Conference Room,International Exchange Bldg. 1F
Cafeteria Fuji, Central Bldg. 2F
Cafeteria Fuji, Central Bldg. 2F
Cultural events:
Reception Hall & Oka Tei,
Scientific events:
International Conference Room,International Exchange Bldg. 1F
Cafeteria Fuji, Central Bldg. 2F
Cafeteria Fuji, Central Bldg. 2F
Athletic Bldg. 1F & B1F

Cultural events:
Reception Hall & Oka Tei,
Scientific events:
International Conference Room,International Exchange Bldg. 1F
Cafeteria Fuji, Central Bldg. 2F
Cafeteria Fuji, Central Bldg. 2F
Large Hall, Arts Bldg. 1F
Reception Hall,International Exchange Bldg. 1F
Cafeteria Fuji, Central Bldg. 2F

13

July 16
SundayJuly 17
Monday7:15-8:00
8:00-19:00

Breakfast
Full-day Kanto Excursion 2

Cafeteria Fuji, Central Bldg. 2F

7:15-8:00
9:30-12:00

Breakfast
Closing Ceremony

12:20-13:30

Farewell Lunch

Cafeteria Fuji, Central Bldg. 2F
Large Hall, Arts Bldg. 1F
Reception Hall,International Exchange Bldg. 1F

Departures

2.6.7 Time table for leaders and observers

IPhO2023 Team Leader & Observer Program
Black: Nippon Seinenkan Hotel
Blue: National Olympics Memorial Youth Center

July 9SundayJuly 10
MondayTime
13:00-17:00

Activity
Registration

17:00-19:00

Get Together

7:00-8:00
10:00-12:00
12:30-14:30

BreakfastOpening Ceremony
Lunch

14:30-18:30

Board meeting (Exp. Exam)

18:30-20:00

DinnerBoard meeting (Exp. Exam)(Cont.)

20:00-23:00
July 11
Tuesday

The dining room on the 9th floor

7:00-8:00

Breakfast
Board meeting (Theory
exam)
Lunch
Board meeting (Theoryexam) (Cont.)
DinnerBoard meeting (Theoryexam) (Cont.)

The dining room on the 9th floor
Rm. Yellow (for leaders)Rm. Blue (for observers)
The dining room on the 9th floor
Rm. Yellow (for leaders)Rm. Blue (for observers)
The dining room on the 9th floor
Rm. Yellow (for leaders)Rm. Blue (for observers)

7:00-8:00
9:00-15:00
18:00-19:30

BreakfastHalf-day Tokyo Excursion 2
Dinner

The dining room on the 9th floor

7:00-8:00
12:00-13:30
16:00-17:40

Breakfast
Lunch
Special Lectures

18:00-19:30

Dinner Party

7:00-8:00
12:00-13:30

Breakfast
Lunch
Board meeting (medal
threshold)
Dinner

12:30-14:00
14:00-18:00
19:30-23:00

July 14
FridayJuly 15
Saturday

The dining room on the 9th floor
Large Hall, Arts Bldg. 1F
The dining room on the 9th floor
Rm. Yellow (for leaders)Rm. Blue (for observers)
The dining room on the 9th floor
Rm. Yellow (for leaders)Rm. Blue (for observers)

BreakfastHalf-day Tokyo Excursion 1
Dinner

18:00-19:30

July 13
Thursday

Reception Hall,International Exchange Bldg. 1F

7:00-8:00
9:00-15:00
18:00-19:30

9:00-12:30
July 12
WednesdayPlace

14:00-15:00
18:00-19:30

The dining room on the 9th floor

The dining room on the 9th floor
The dining room on the 9th floor
The dining room on the 9th floor
Large Hall, Arts Bldg. 1F
Reception Hall,International Exchange Bldg. 1F
The dining room on the 9th floor
The dining room on the 9th floor
Rm. Yellow (for leaders)Rm. Blue (for observers)
The dining room on the 9th floor

14

July 16
SundayJuly 17
Monday7:00-8:00
9:00-12:15
12:15-13:30
13:30-16:45
18:00-19:30

Breakfast
Moderation
Lunch
Moderation (Cont.)
Dinner

20:00-23:00

Final Board Meeting

7:00-8:00
9:30-12:00

Breakfast
Closing Ceremony

12:20-13:30

Farewell Lunch

The dining room on the 9th floor
Rooms on the 8th floor
The dining room on the 9th floor
Rooms on the 8th floor
The dining room on the 9th floor
Rm. Yellow (for leaders)Rm. Blue (for observers)
The dining room on the 9th floor
Large Hall, Arts Bldg. 1F
Reception Hall,International Exchange Bldg. 1F

Departures

2.6.8 Ceremony programs

Opening Ceremony

July 10 (Mon)
Opening Address
KOBAYASHI Makoto (Chair, Organizing Committee of IPhO2023)
Congratulatory Address
NAGAOKA Keiko, Minister of Education, Culture, Sports, Science, and Technology
Contestants Introduction
Each team of contestants called onto the stage
Address
RAWAT Rajdeep (President, IPhO Secretariat)------------------Welcome Events (Stage Performances)
Wadaiko (Japanese drum)
International Christian University Wadaiko Club
Karate demonstration
Sophia University Karate ClubSpecial Lectures July 14 (Fri)[Lecture 1] “Neutrinos – key particles for the understanding of the smallest particles andthe largest Universe –"KAJITA Takaaki, Distinguished University Professor, The University of Tokyo,
2015 Nobel Laureate in Physics[Lecture 2] “Don’t waste your gifted talents”
AMANO Hiroshi, Professor, Nagoya University, 2014 Nobel Laureate in Physics
Moderator: YOKOYAMA Hiromi
Professor, Kavli Institute for the Physics and Mathematics of the Universe.
The University of Tokyo

Closing Ceremony

July 17 (Mon)

Opening address
KOBAYASHI Makoto (Chair, Organizing Committee of IPhO2023)
Report on the Implementation of Examination
HAYANO Ryugo (Chair, Academic Committee of IPhO2023)
Announcements
IYE Yasuhiro (Chair, Executive Committee of IPhO2023)

15

Presentation of Diversity Commendation
Presenter:
YOKOYAMA Hiromi
Medal Ceremony, Special Awards
Medal Presenters: RAWAT Rajdeep, STANKEY Paul, SAKAIKI Hiroyuki
AMANO Hiroshi, KAJITA Takaaki, KOBAYASHI Makoto
Greeting from the Next Host Country
SHIRZAD Ahmad (Chair, Organizer of IPhO2024 in Iran)
Closing Remark
RAWAT Rajdeep (President, IPhO Secretariat)-----------------------------Farewell Events (Stage Performances)
Koto (Japanese horizontal harp) Music
Sophia University Koto Club
Daikagura (Japanese traditional street performance)
Daikagura Kyokugei Kyoukai

2.6.9 Closing of IPhO2023
In the Closing Ceremony, the Academic Committee Chair HAYANO made a presentation explaining theexam problems and the distribution of contestants’ scores. Special awards “Diversity Commendation” were
given to four teams which exhibited both healthy gender diversity and respectable contest results.
That was followed by the announcement of the winners of Honorary Mentions, Bronze Medals, Silver
Medals and Gold Medals. Bronze medals were presented by the IPhO President RAWAT Rajdeep, theIPhO Secretary STANLEY Paul and the Fundraising Committee Chair SAKAKI Hiroyuki. Silver medals by
the Organization Committee Vice-Chairs AMANO Hiroshi and KAJITA Takaaki, and Gold medals by theOrganization Committee Chair KOBAYASHI Makoto. Finally, the Best Performers in the experimental examand the theoretical exam, and the Absolute Winner were announced and given the respective trophies. It
turned out that two contestants tied at full marks in the theoretical exam. An additional piece of trophy was
made and sent to the one of them after IPhO2023.
After the presentation of medals and prizes, Iranian Leader SHIRZAD Ahmad made an invitation addressof IPhO2024 in Isfahan. The official part of the Closing Ceremony was concluded by a closing speech by
the IPhO President RAWAT. After that, “koto (Japanese horizontal harp)” music played by a student clubof ICU and “daikagura (juggling performance)” by professional street performers entertained the audience.
After the Closing Ceremony, a farewell lunch party was held.
The representatives of the individual teams were urged to visit the IPhO2023 headquarters to pick up
such documents as “Certificate of Participation”, “Certificate of Medals (or Honorable Mention)”.
Delegations were sent off and transported to the airports as necessary to catch their return flights.

2.7 Post-Event Works
2.7.1 Experimental kits
After the experimental exam, the experimental kits used by the contestants were repacked by the staff
and student supporters. We gave one set of the used kit to each of the participating country/region for free.
For those teams or individuals who wanted more than one set, we sold brand new kits at a price of
80,000JPY/set which was an actual cost. Prior to IPhO2023, we had planned to sell used kits at a reduced
price. However, the condition of the experimental kits after use differed significantly from one to another,and we did not have time or manpower to confirm their operation. Therefore, we decided to give them forfree with the following priority order. Those teams who had signed up to buy used kits at the time of teamregistration were awarded the first priority. Those teams who bought brand new kits were given the same
number of used kits for free. The remaining kits were distributed to the other teams by lottery. Thus, wesold 20.5* sets of brand new kits and gave away about 200 sets of used kits to the participating

16

countries/regions. ( *One set of the experimental kits consisted of two boxes of apparatuses corresponding
to the two experimental exam tasks.)
The remaining kits were distributed to some 100 “Super Science High Schools (SSH)” which are highschools designated by MEXT for special science education, to be used for their physics education.
2.7.2 Questionnaire survey
A week after the closing of IPhO2023, we conducted an on-line questionnaire survey to the participantsof their impression, evaluation and other opinions about IPhO2023. Two kinds of Questionnaire Form
(Google form), one for the students and the other for the leaders and observers, were prepared and sent
to the leaders and observers of all participating teams. Since we did not collect the e-mail addresses ofstudents, we asked the leaders to forward to their students the letter requesting cooperation to the survey.
By the end of August, we got response from 79 students and 76 adults. The questionnaire answers are
summarized in Chapter 7 “Feedbacks from the Participants”.

17

3. Preparation and Implementation of IPhO2023 Examination
3.1 Composition of the Academic Committee
As indicated in Figure 1 the organization of the IPhO2023 includes the Academic Committee highlighted
in yellow. Enclosed by the dotted orange line is the team primarily responsible for the development of theexam problems. Following the Organizing Committee's inaugural meeting in May 2016, the Academic
Committee initiated its activities. The identities of the committee members were kept confidential, with the
exception of the Chair, up until after the conclusion of IPhO2023, when the full membership was revealed.
The committee consisted of eight members from the theoretical subcommittee, six from the experimental
subcommittee, and one individual assigned to handle English translations and proofreading. The
Invigilation Subcommittee was in charge of overseeing 70 invigilators, whereas the Chair of the Marking
Subcommittee was responsible for managing the recruitment and coordination of 46 markers.
It was important to delineate that the Committee of Japan Physics Olympiad (JPhO), responsible for thenational selection and training of contestants for each year’ IPhO, operated autonomously from theAcademic Committee. A strict information barrier was maintained between the two organizations from thestart.

Figure 1 Composition of the IPhO2023 Academic Committee

3.2 Academic Timelines
Table 1 shows the timeline of the activities related to the Academic Committee from its establishment
during the preparatory phase of IPhO2023. Table 2 shows the schedule for students, leaders, Academic

18

Committee members and markers during IPhO2023.
Table 1 Major timeline for Academic Committee until IPhO2023
May
July

2016
2016

Sept 2016
July
2017
March 2018
April 2018
July
2018
July
2019
Feb
2020
May 2020
Oct

2020

Nov
2020
July
2021
March 2022
June 2022
Aug
2022
Sept 2022
Jan
2023
March 2023
April 2023
May13 2023
June 2023
July 1 2023
July 9 2023

Table 2

Steering Committee, Academic Committee, Fundraising Committee established.
HAYANO attended IPhO2016 as an observer.
Started recruiting Academic Committee members.
Started researching past IPhO problems.
Steering Committee chair (IYE) attended IPhO2017 as an observer.
Completed the report on analysis of past IPhO problems.
Started brainstorming for problem ideas (initial focus on experimental problems).
Sent an Academic Committee member as an observer to IPhO2018.
IYE attended IPhO2019 as an observer.
COVID-19 → We switched to online meetings via Zoom.
IPhO2020 (Lithuania) postponed to 2021,
IPhO in Japan postponed from 2022 to 2023.
Selected and contracted with manufacturers for mass production of experimental
equipment.
Started discussions with Tokyo City University about design of exam booths.
HAYANO and IYE served as Invigilators for IPhO2021 (online, hosted by Lithuania).
Separated theory and experiment sections of the Academic Committee.
Evaluated the theory problems (the 5 final candidates) by 3 monitors.
Evaluated the experiment problems (the 3 final candidates) by 3 monitors.
Selected 3 theory problems (1 backup) and 2 experiment problems.
Started translating the problems into English.
Began preparing model answers and marking schemes.
Signed a contract with the OlyExams Association.
The IPhO2023 Organizing Committee decided to hold IPhO2023 in a face- to-faceformat.
Started recruiting marker teams.
Conducted a mock exam and marking practice on the day of the IPhO President’s visit.
Registration of leaders and students.
IBM rehearsal.
Rehearsal for conducting the exam.

IPhO2023 schedule
Students

July 10

Leaders

Academic Committee

Markers

Opening Ceremony
IBM: Discussion of exp. Exam questions

July 11

Translation
Printing of problems
Exp. Exam

Excursion

Administer the exam
Scanning of answer sheets

July 12Excursion

July 13

IBM: Discussion of theory exam questions

Exp. Exam marking

Translation
Printing of problems
Theory Exam

Excursion

Administer the exam
Scanning of answer sheets

July 14

Excursion

Marking

Theory exam marking

19July 15

Excursion

Score disclosure
IBM: determine medal thresholds

July 16

ExcursionModeration
IBM: determine medalists

July 17

Closing Ceremony

3.3 Making of IPhO2023 Exam Problems
3.3.1 Preparatory phase
In the midsummer of July 2016, we commenced our strategic journey towards the International Physics
Olympiad, with the Academic Committee Chair HAYANO, who notably had no prior IPhO experience,
attending IPhO2016. His participation was aimed at gaining a deep understanding of the competition's
operations. This proactive step marked the beginning of an informed series of engagements with the
IPhO events.
In the following years, our engagement with the competition deepened. The Executive Committee Chair
and Secretary General IYE represented our commitment by attending both IPhO2017 and IPhO2019.
Another Academic Committee member attended IPhO2018, further enriching our collective
understanding of the event. The experience was further expanded when HAYANO and IYE served as
invigilators for the 2021 online IPhO hosted by Lithuania, providing us with vital insights into the
management of the Olympiad in a virtual format.
Initiating regular meetings of Academic Committee from September 2016, we set out to scrutinize thepast exam problems, starting with those for IPhO2006 up to the most recent ones. These discussions,which continued until the spring of 2018, focused on assessing the alignment of the problems with the
IPhO syllabus and the overall difficulty and quality. This thorough analysis was critical for cultivating a
consensus among committee members regarding the nature of problems befitting the Olympiad's
standards.
By April 2018, the evolution of our preparation entered into a constructive phase, concentrating on thedevelopment of experimental exam questions. Acknowledging the urgency of manufacturing 500 sets ofexperimental kits, the team prioritized the development of experimental apparatuses. Prototypes were
meticulously crafted and evaluated within the team. For security purposes, we resorted to the use ofpassword-protected Slack channels for communication, while avoiding email correspondences to guard
against information breaches.
As we advanced, our meetings, held approximately every two months, became more comprehensive,
encompassing discussions around both theoretical and experimental problems. However, theunforeseeable advent of COVID-19 in spring 2020 forced us to adapt swiftly, transitioning to virtual
meetings via Zoom. This change represented our flexibility and commitment to ensuring our preparatory
efforts were not derailed by the pandemic.
The implications of the pandemic also led to a rearrangement of the anticipated IPhO schedule. In May
2020, the IPhO Board made the difficult decision to postpone the IPhO2020 in Lithuania to the following
year. As a ripple effect, the IPhO we were set to host in Japan was subsequently moved from 2022 to2023. This rescheduling demanded from us not just patience but also a recalibration of our plans andstrategies to stay on course for the forthcoming Olympiad.
3.3.2 Quality control of exam questions
In March 2022, we streamlined our examination preparation process by dividing the Subcommittee into
two specialized groups: the Theory Subcommittee, comprising 8 members, and the Experiment
Subcommittee, including 6 members. At the division's inception, the theoretical and experimental

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problem pools consisted of five and four candidates, respectively, with three experimental problems
being advanced to the stage of prototyping for mass production. Collaborative joint meetings were
subsequently organized to ensure synergy and coordination between both subcommittees.
A pivotal moment in quality assurance was on June 26, 2022, when we conducted a rigorous monitoring
test of the theoretical problems. For this critical evaluation, three former IPhO students, of whom one
was a gold medal laureate, undertook the challenge of solving five sets of candidate problems, eachcontaining three questions, within a five-hour time frame.
Parallel to this, an evaluation of the experimental problems was executed on August 7, 2022. The
monitors, during a similar five-hour window, were tasked with resolving three candidate problems, eachcomposed of two questions.
In the aftermath of these comprehensive tests, and with the reassurance that there was no content
overlap with the IPhO2022 problems, the month of August 2022 saw the Academic Committee members
cast their votes to select the final problems: three theory problems and a single backup problem,
alongside two experiment problems. It is worth noting that all preparatory steps were conducted using
the Japanese language.
3.3.3 Mass production of experimental equipment
Identifying a manufacturing partner that could ensure the bulk production of 500 experimental
equipment kits within financial bounds was a critical milestone achieved in October 2020 with Shimadzu
Rika, a Shimadzu Corporation subsidiary experienced in crafting physics educational tools. The
partnership commenced with the mutual agreement on confidentiality.
Until March 2023, the status of the competition's format—whether it would be held remotely or inperson—remained uncertain, prompting considerations for the ease of equipment shipping. The
equipment had to be designed for safe transportation, potentially across borders, and adhering toregulatory standards such as the Restriction of Hazardous Substances (RoHS).
This period of contingency planning concluded when the Organizing Committee confirmed the on-site
execution of IPhO2023 in March 2023.
Prototyping and cost assessment of three experimental devices were completed by August 2022,
leading to the selection of two final designs geared towards mass production: a device based on the
Kibble balance concept and another for measuring sample thickness using birefringence. We thenproceeded with the mass production phase.
Innovation was integral in the development phase. The Kibble balance apparatus incorporated a 3Dprinted oscillator, which efficiently provided a lightweight and low-cost solution. For the birefringenceexperiments, the prototyping phase initially used expensive commercial optical components. However,post-prototyping, we identified cost-effective manufacturing methods using cardboard and synthetic
wood that maintained optical precision, significantly reducing production costs.
3.3.4 Recruiting the markers
IPhO2023 deployed an innovative marking system, diverging from the conventional method whereindividual teams would grade each problem. Historically, assembling 80-90 markers to address thepapers from participants across 80 nations was a commonplace practice. Yet, IPhO2023 coincided withthe summer term at universities in Japan, which posed a significant challenge in sourcing an adequate
number of markers.
Consequently, we adopted a more streamlined approach where each team, comprising a pair ofmarkers, was responsible for assessing all submissions (two experiments and three theories) from 3-4
specific countries. This restructuring led to a formation of 20+ such teams. While this new model placeda higher workload on the markers, given that it required engagement on both experimental andtheoretical grading days, it offered improved manageability and quality control measures, ensuringconsistent application of the marking criteria as all markers were centralized in one location.
Moderation also changed, with leaders and markers at each table reviewing all problems together for 1

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hour and 40 minutes, which simplified the schedule.
For the staffing needs, we onboarded 23 postdoctoral researchers alongside 23 graduate students—
among whom were former IPhO contestants—from the University of Tokyo’s Graduate School of Physics.
This (23 instead of 20 teams) was a precautionary measure in anticipation of potential absenteeism due
to COVID-19, which, fortunately, did not materialize. These individuals made up the 23 marking teams.
3.3.5 Rehearsals
At the onset of 2023, we entered into a partnership with the OlyExams Association, embracing the useof ExamTools for managing the myriad aspects of examination administration—from handling source
files for problems, translation, and printing, to the scanning of answers sheets and overseeing the IBM.
A notable assembly was on May 13, in conjunction with the visit from the IPhO President. That day, the46 markers convened; each was allocated a problem to solve in the morning session. Subsequently, theAcademic Committee members elucidated on the marking schemes in the afternoon, and the marking
teams engaged in a hands-on marking exercise with the answer sheets from the morning's mock exam.
The feedback and variability observed during this marking session were crucial in refining the marking
schemes.
Further, on July 1, we conducted an IBM rehearsal, which was well-attended by members of the
Academic Committee, the technical support staff, and the secretariat. The team from OlyExams provided
a demonstration of how to operate the IBM via ExamTools, supplemented by a practical session for theattendees. Additionally, we executed a test stream of the IBM session using Zoom and undertook acomprehensive assessment of the network environment and its throughput capabilities.
On the eve of the opening ceremony, July 9, a final rehearsal encompassed all personnel, including
part-time staff, which simulated the complete examination procedure. This drill covered all proceduralelements such as the printing and transport of exam booklets, distribution at the test site, execution of
the examination, responding to students’ requirements, collecting answer sheets, and their precise
scanning, thereby ensuring a smooth operation on the day of the actual exam.

3.4 Other Preparatory Tasks
Executing the exams involved significant preparation beyond problem creation, with the
Academic Committee Chair overseeing several key tasks:
3.4.1 Choosing the venues
The National Olympics Memorial Youth Center (NYC), initially chosen for student housing and the examvenue, posed significant challenges. Necessary were accommodations for leaders/observers completely
separated from students, a location for the board meeting, a marking area, and a secure, high-bandwidthinternet environment. Given these constraints, a reassessment led to the following decisions by January2022:
 NYC would house students, provide exam facilities, and serve as IPhO2023 headquarters.
 The Nippon Seinenkan Hotel (NSH) would accommodate leaders/observers and hold board
meetings.
 The University of Tokyo Institute of Industrial Science (IIS) campus would facilitate marking andlarge volume printing/scanning.
With these venues located within a 2 km radius from the NYC (Figure 2), logistical continuity for secure
exam material transport was established.

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Figure 2 Locations of IPhO2023 venues

3.4.2 Exam booths
The Cooperation with Tokyo City University's Department of Architecture led to exam booth designs,
initiating in November 2020 and culminating in mass production by April 2023. The final design included:
 Assembly-style booths for 450 participants across two gymnasiums in NYC, devoid of electrical wiring(this means that all exam equipment must be battery operated).
 Use of existing gym lighting, supplemented by booth white walls, to ensure desk illumination.
 Desks sized 150-180cm by 60-80cm, determining the limit for exam apparatus sizes.
 Aisle clearances for safety and invigilation.
After prototyping, a white-walled, 1.6m height booth model was chosen. Necessary accessories such as"Water, Toilet, Help" flags and procedural guidelines were developed for the booth setup at NYC by July 7.
Additionally, surveillance systems were installed in the exam halls and auxiliary printing facilities were
established adjacent to the exam hall 1 (Figure 3 and Figure 4).

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Figure 3 Exam venue floor layout

Figure 4 Booths closeup
3.4.3 Student codes and booth codes
Once registrations were completed, we allocated student codes and booth codes for participants. The
structure of assigning codes was as follows: Student Codes: These codes comprised a three-letter country code, followed by an 'S' for "student,"
and a serial number. For example, "JPN-S-1" represents the first student from Japan.
 Booth Codes: Each exam booth was designated by its location, with codes indicating the Row (Athrough V) and the Column (1 through 27), such as "Q-14."

24

Using a random number table, we matched exam booth codes with student codes. Figure 5 displays
the layout for Exam Room 1 on July 11, set for the experimental exam, including specified booth rows
and columns. For the theory exam on July 13, we used a different set of randomized numbers to generatea new seating chart.
Each student's nametag exhibited both their student code and their booth code — these identifiers werealso displayed on exam booths to direct students to their respective seats. Furthermore, student andbooth codes were printed on the exams' envelopes, visible through a window, allowing invigilators toensure that each envelope reached the correct booth (Figure 5).
For added security and organization, QR codes were printed on all answer sheets and worksheets(illustrated in Figure 6). These codes were instrumental in ExamTools' feature of sorting scanned images
into dedicated folders for each participant and question as soon as they were scanned.

Figure 5 Exam Room 1 Booth Layout for the Experimental Exam

Figure 6 Student & Booth codes used in the exam problem packages

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3.4.4 Exam tools
Our engagement with OlyExams for the use of their ExamTools commenced in the spring of 2021.
Several Science Olympiads, across various disciplines, have utilized ExamTools since its introduction
at IPhO2016. The platform managed an array of tasks — from handling exam question source files,
overseeing translations and printing, to scanning and facilitating IBMs.
The ExamTools were operated and maintained by the OlyExams team based in Switzerland, with thesystem hosted on a cloud server in France. Approximately 2.5 months prior to IPhO2023, the Academic
Committee began uploading the question source files and reviewing the output PDFs generated by thesystem.
Our communication with the OlyExams team was primarily conducted via Slack, supplemented with
Zoom meetings as necessary. Although there was an option for the OlyExams team to provide on-site
support in Japan, the effectiveness of remote assistance negated the need for their physical presence
during the Olympiad.
Throughout IPhO2023, the OlyExams team delivered round-the-clock support in two shifts. A fourperson team provided first-level network and ExamTools technical support to leaders engaged in theIBM. An individual was also dedicated to overseeing the technical aspects of the print servers located in
the Bulk Print Center.
3.4.5 Designing the IT infrastructure
For IPhO, the meticulous design of the network, printers, and other facets of IT infrastructure wascrucial, alongside comprehensive staff training and rigorous pre-event testing. The following components
were of particular significance: Network Configuration at the IBM Venue
 Strategic Printer/Scanner Placement
 Secure Video/Audio Streaming Capabilities
Each element is elaborated upon in the subsequent sections.
IBM venue setup
Ensuring the stable operation of ExamTools from the setup phase through the conclusion of IPhO2023
was paramount. Specifically, leaders and observers required stress-free access, with sufficient
bandwidth, to ExamTools for the translation of exam questions via the venue's Wi-Fi. Achieving this levelof service was challenging from a network design standpoint.
We secured the entire 8th floor of the NSH for the IBM (Figure 7). The allocation of rooms on this floor
was as follows:Room Yellow (250 m²): Served as the central hub for approximately 160 leaders, academic
committee members, and support staff.
Room Blue (140 m²): Designated for observers as Room Yellow could not accommodate everyone.

Room Green (70 m²): Utilized for the experimental equipment showcase on the IBM's first day andas the organizing committee's operational area on subsequent days. At the entrance, a high-speed
printer was placed for use by leaders and observers.
Room Orange (40 m²): Operated as the academic committee's workroom, outfitted with high-speed
printers (one operational and one backup) and a PC print server.
To accommodate nearly 300 individuals connecting to Wi-Fi over a 500 m² space, we installed two
1Gbps optical lines, in addition to the hotel's existing line. We ensured traffic balancing and redundancy
by contracting these lines from different providers. The Wi-Fi mesh setup comprised multiple Yamaha
WLX413 units, capable of supporting 500 PC connections each, which met the high demand anticipatedfor IPhO2023's IBM (Figure 7). Additionally, PCs for print servers and three high-speed printers(including one ready on standby) were deployed.

26

Figure 7 Floor layout and network configuration of NSH 8F (IBM venue)
Printers/scanners
Figure 8 outlines the distribution of printers across the three IPhO2023 venues. We standardized theprinter model for consistency and efficiency, opting for the Kyocera TASKalfa 5054ci (printing speed of
50 pages/minute, scanning speed of 130 pages/minute), a smaller Kyocera ECOSYS P5026cdw printerwas situated adjacent to Hall-1 for supplementary worksheet printing needs.
At the NSH venue, printers were made available for the Academic Committee's exclusive use (print
queue “Orange”) and for self-service by team leaders and observers (print queue “Green”). The Bulk
Print Center at Tokyo University's Institute of Industrial Science (IIS) encompassed a print server PC
running Ubuntu and a quintet of Kyocera TASKalfa 5054ci printers, all integrated into the campus
network.
The setup and software installation for the Bulk Print Center’s server PC was handled remotely from
Switzerland by the OlyExams team. Extensive testing, including a mock exam and marking session
conducted on May 13th, helped us gauge the printers' throughput. These trials, coupled with projectionsof the printed sheet volume and the event's time constraints, prompted the decision to utilize five printers
for efficient operation (instead of four, as was initially planned).

27

Figure 8 Printer configuration
Enhancing Connectivity Through Zoom at IPhO2023
During IPhO 2023, Zoom functioned as a crucial communication bridge connecting various locations.
The IBM session, conducted in Room Yellow, was seamlessly relayed to Room Blue, which served as
the observer's space, Room Orange, reserved for the Academic Committee members, and the
OlyExams team based in Switzerland. Access to Zoom was securely gated, requiring authentication
through the email addresses registered for IPhO2023. Notably, access from outside Japan was restricted
to prevent unauthorized entry, with a sole exception granted to the OlyExams team for operational
purposes.
In instances where local support teams, stationed in room Yellow, found themselves unable to resolve
certain issues, such as difficulties encountered in the translation of problem texts, they were afforded theability to seek immediate assistance from the OlyExams team. This support utilized a dual-channel
approach, involving both Slack and Zoom.
Moreover, Zoom was deftly integrated with the IIS print center, the grading site, and the NYC exam
site, enabling real-time monitoring and status updates across these crucial nodes. This integration
proved instrumental in streamlining coordination and ensuring the smooth running of the event.
The IT operational framework is illustrated in Figure 9. It highlights the constant surveillance of the
Wi-Fi traffic and fiber optic loads at NSH (depicted in the left panel of the figure). During the IBM sessions,the technical operators were tasked with managing microphones, controlling a remote video camera,28

and distributing the feeds to Zoom, ensuring the event's technological aspects ran smoothly (right).

Figure 9 (left) Constant monitoring of the Wi-Fi traffic load at NSH.
(right) An audio-visual operator at the IBM site.

3.5 International Board Meeting (IBM)
According to IPhO regulations, up to two leaders from each country may participate in IBM. Althoughobservers were welcome to attend the meeting to translate the test questions and to grade the answer
sheets of their national contestants, they did not possess voting rights. This gathering was held at the NSH,
which also served as the residence for the leaders. The event saw 81 official participating countries joinedby one observer country, with attendance totaling 156 leaders and 97 observers
3.5.1 Discussion and decision of exam questions
On the afternoon of July 10th, the Board convened to finalize the examination questions. The Academic
Committee presented two questions, and the setup needed for the exam was demonstrated. An
instructional video detailing the assembly of this equipment was also shown.
Shortly after the IBM began, concerns were raised about the length of the examination questions. The
Academic Committee was aware of the IPhO regulation that "the text of the theoretical and experimental
examinations shall not exceed 12,000 characters each, including spaces and excluding the cover sheet
and answer sheets". They had been careful to ensure that the number of characters for each question
did not exceed this limit. The committee was also aware of past instances where IPhO questions had
exceeded 12,000 characters. However, during the IBM it became clear that the wording of the rules had
been interpreted in the past to mean that the 12,000 character limit was intended to apply to the total
character count of all questions combined, for both theoretical and experimental papers. This deviationfrom the Committee's understanding was further highlighted by the fact that the IPhO President's visit in
May had not served to clarify this interpretation. When the issue was raised at the beginning of the IBM,
there was an immediate need to address the situation. It became imperative to quickly revise andcondense the examination text on the spot to conform to the practiced and historical interpretation of the
12,000 character limit.
Responding swiftly, the Academic Committee condensed the text, and the final version of the twoquestions in English was approved at 1:00 following a vote. Translations were completed by 4:30.
On July 11, the day before the second IBM meeting where the theory problems were to be reviewed,
efforts were made to reduce the number of characters in the theory questions. In many cases theintroductory part had to be removed and/or some problems had to be taken out.
At 8:00 a.m. on July 12, the shortened versions were distributed. Moderated by the Theory Subcommittee
Chair ITOH, the discussions proceeded without hindrance, culminating in the official English versions of29

the three questions being voted on and approved at 22:00. The translation process was completed around3:00.
3.5.2 Marking and medal thresholds
After each examination, answer sheets and worksheets were returned to leaders at the NSH by 8:00.
the following day. At the same time, scanned documents were uploaded onto ExamTools. The leadersof each delegation graded their students’ answers based on these materials.
Scores from the organizers were shared with each team via ExamTools on July 15th, prior to the IBM
where medal thresholds were established. The Chair and Vice-Chair of the Academic Committee had
exchanged views with the "Three-Person Committee" (as defined in Regulations to §7 of Statutes) on grading, inparticular how to award partial marks and how to deal with errors in answers that carry over to later questions. The
Chair then confirmed that they would follow the "Three-Person Committee's" suggestions.
The day before the moderation was scheduled, quarantine measures were implemented due to COVID19 infection cases among a few leaders and observers that had occurred at the NSH. HAYANO addressed
this issue at the International Physics Olympiad Board Meeting (IBM) on July 15th, stating that participationin the moderation session scheduled on the following day would be restricted to two representatives fromeach delegation. Furthermore, it was mandated that attendants (both markers and leaders) test negativein antigen tests and wear masks during the event. Antigen tests for more than 200 participants of themoderation (i.e. 46 markers, 160 leaders (or observers, if the leader turns out to be positive) and 20
members of the Academic Committee) had to be finished before 9 a.m. To meet this need, a sufficientquantity of antigen test kits which would give the result quickly, had to be collected in a hurry and werepurchased in the middle of the night of the previous day at several local pharmacies by the Executive
Committee. Fortunately, almost all attendants were confirmed negative before the deadline for the start ofthe moderation.
For countries/regions whose leaders tested positive for antigen, it was decided to conduct the moderation
via ZOOM. The moderation for the team of individuals was set in a separate room at the NSH after they
were confirmed to be antigen negative.
3.5.3 Moderation
The moderation took place on July 16th, spanning from 9:00 to 16:45 in two separate rooms of the NSH,
Yellow and Blue. Here, pairs of markers were seated across from pairs of country leaders at each of the
23 tables provided. Each country/region was allocated a total time of 100 minutes for discussion, split
across two morning sessions and two afternoon sessions.
Leaders would naturally negotiate with moderators with the goal of raising the scores of students who
may be a little closer to earning a better medal. However, if there were a large number of cases wheremoderation raised scores, it could lead to medal inflation. Therefore, the Academic Committee had
instructed the markers to carefully read not only the answer sheets, but also the worksheets, and to add
points in favor of the students to the extent that it is not unreasonable in light of the scoring criteria. They
were then instructed to increase the score during the moderation session only in cases where marking
errors were obvious.
Most moderation proceeded without problems. However, some leaders continued to negotiate beyond
the allotted 100-minute window for the solution to a particular problem for a particular student. In suchcases, the "Three-Person Committee" on site intervened. In some cases, when consensus could not bereached, the committee took the average of the moderator's and leader's arguments and awarded points
in 0.05 increments. This procedure is vaguely noted in Marking Rules 4.5 in the IPhO's regulations, but
is not explicitly stated, but it was an unavoidable measure since moderation could not be prolonged
indefinitely.
3.5.4 Medal decision
The final board meeting of the competition was held on July 16th at 20:00. The agenda related to the30operation of the IPhO was discussed, and it was decided that the next competition would be held in Iran.
The medal winners were then announced, with 37 gold medals, 74 silver medals, 103 bronze medals, and54 honorable mentions awarded out of the 393 participating contestants. Additionally, four countries(Cyprus, France, Iceland, and Ukraine) were commended for their diversity in participants and excellent
results. The closing ceremony, where the winners received their medals and prizes, took place on the 17that NYC.

3.6 Conducting Exams
This section details the logistics, i.e. activities behind the scenes, of conducting exams and their marking
on schedule, which was a rase against time.
3.6.1 Printing works at IIS venue
The final draft of the experimental exam was completed just after midnight on July 10th during the IBM,
causing subsequent delays in the translation of the questions. The translations were not completed until
5:00, creating a logistical challenge to meet the 6:30 deadline for the printing team to ship the exam
materials to the NYC venue. The English version of the exam was 65 pages, including General
Instructions (1 page), Experiment 1 (22 pages total: Cover 1, Questions 9, Answer Sheets 12, Worksheets
10), and Experiment 2 (32 pages total: Cover 1, Questions 12, Answer Sheets 9, Worksheets 10). The
translated versions varied in length, with some exceeding the page count of the English version. In
addition, some countries provided their students with both the English original and the translated versions,
resulting in an estimated total of approximately 40,000 printed pages.
For the Theory Exam, the final draft of the English version was completed efficiently, with all teams
completing their translations by approximately 3:00. Printing began just before midnight on July 12th, anddelivery to the NYC venue was completed by 6:00. The English version of the Theory Exam consisted of
73 pages, including General Instructions (2 pages), Theory 1 (26 pages: Cover 1, Questions 6, Answer
Sheets 4, Worksheets 15), Theory 2 (23 pages: Cover 1, Questions 5, Answer Sheets 2, Worksheets 15),and Theory 3 (20 pages: Cover 1, Questions 4, Answer Sheets 2, Worksheets 15). The estimated total
number of printed pages was approximately 45,000.
3.6.2 Test administration work at NYC venue
The experiment exam was administered on July 11 from 9:00 to 14:00. The envelopes containing
questions, answer sheets and worksheets were delivered from IIS to the NYC venue, and the invigilators
distributed them to the booths. Students entered the exam booths at 8:30. Although they were informed inadvance that they were not allowed to bring their personal belongings, many students disobeyed the ban
and were forced to leave them at the entrance of the exam halls. Because it is difficult to individuallycheck whether a wristwatch has communication capabilities, students who are wearing a wristwatch were
instructed to remove it and place it outside the booth.
Figure 10 (left) shows Help, Water and Toilet flags placed at the entrance of the exam booth, andFigure 10 (right) shows stationery (a ballpoint pen, a mechanical pencil, refills, an eraser, and a ruler),
an official calculator, a radio-controlled clock, a bag of snacks, and a water bottle provided by theorganizers for the students.

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Figure 10 (Left) “Help”, “Water”, “Toilet” flags placed at the entrance of the exam booth.
(Right) Stationery, snacks, and water provided by the organizers for the students.
When the exam started at 9:00, some students asked for help because they found some sheets missing,or they noticed that the booth numbers did not match the names displayed (this had been a problem during
registration by the participating countries).
Several students short-circuited the power supply without fully reading the instructions in the question
text and blew the power supply fuse in Experiment 1. This could be considered a failure of question 1.
However, we decided to help them; Shimazu-Rika personnel involved in the production of the equipment
were on standby at the test site in case this happened, and responded by replacing the power supply.
Otherwise, there were no major problems that affected the administration of the exam.
The exam ended at 14:00. The students were instructed to sort all the sheets (problems, answer sheets
and worksheets) and put them in the envelopes. After forbidding the students to take anything on theirdesks, the exam questions and answers were collected and after confirming that everything had beencollected, they were sent to the IIS venue before 15:00.
The venue was then cleaned and prepared for the theoretical exam on the 13th. The experimental setups
were repackaged and transported from NYC to NSH for distribution to the leaders.
The theory exam was similarly conducted on July 13 from 9:00 to 14:00. During the exam, some students
attempted to take the exam questions and answer sheets out of the venue despite the ban. The invigilators
made every effort to find such cases and retrieve the removed papers. But there were still dozens ofpages that could not be retrieved and resulted in “missing” errors when the answer sheets were scanned.
In such cases, we printed a new page with a QR code, as shown in Figure 11, inserted it to the respective
place of the answer sheets, and informed the markers that the page could not be retrieved.
Some other students complained about incomprehensible exam questions, which they believed to betranslation errors made by their leaders. When such a student requested the official English version tocheck the meaning of the question, we took steps to inform the student that the English version would only
be distributed if the leader specified that both the translated version and the official English version be
printed. Since there were a significant number of requests for the English version, it may be better to
distribute the official English version to all students in future IPhOs to make the test administration smoother.
However, this will increase the number of printed copies of the questions and thus the workload for the
printing team.
The exam ended at 14:00 and the envelopes were collected and sent to the IIS site at 15:00. Students
were allowed to take all items on the desks with them.

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Figure 11 How missing page(s) were handled.
3.6.3 Scanning and copying work at IIS venue
After the experiment exam, the envelopes arrived at IIS from NYC shortly after 15:00. And were scannedby a 10-person scanning team. Members of the Academic Committee checked the scanned data forcorrect storage in the ExamTools folder. However, some worksheets could not be found despite
considerable efforts to locate them (presumably students had taken them home), and in these cases a“missing page” was inserted with the Academic Committee Chair’s signature.
After scanning, the team printed two copies of the answer sheets+worksheets from ExamTools, one forthe scoring team and the other for the leaders. The total number of pages printed was estimated to beapproximately 35,000.
The original answer sheets were given to the 27 part-time helpers. They read the handwritten numbersin the table and the students' experimental results, as illustrated in Figure 12, and typed them into thedesignated Excel sheet.
A macro on the Excel sheet sorted those numbers in order (often out of order, since the students tended
to measure back and forth), compared the results to the marking criteria, and color-coded them toindicate whether they were within the range considered correct. On July 12th, the markers first lookedat the Excel table for scoring, and then checked the original handwritten number table if there was any
doubt. This greatly sped up the marking process.

Figure 12 (left) A typical handwritten table from an Experimental Exam answer sheet.
(right) converting the handwritten tables to Excel sheets

33

The scanning/printing of the theory exam answer sheets/worksheets was done in a similar manner,except that the theory exam did not require Excel spreadsheet entry. The printing (copying) consisted of
53 pages of answer sheets and worksheets, and the total number of printed/copied pages was estimatedto be approximately 43,000.
3.6.4 Marking
Marking sessions began at the IIS the day after each exam. To facilitate the process, a member of the
Academic Committee was present to provide a detailed explanation of the marking protocol and toanswer any questions that arose. Following a regimented procedure, each answer sheet was marked
independently by a pair of markers from the respective teams. To clearly distinguish the entries, the firstmarker used a red pencil to indicate areas warranting partial credit and to record the preliminary score,
while the subsequent marker used a blue pencil. After completing their individual evaluations, themarkers met to reconcile any discrepancies in scoring and discussed until a consensus was reached.
Only then did the markers sign off on the answer sheets. These final grades were then entered into
ExamTools. Marking took place on July 12 and 14, from 9:00 a.m. until late in the evening. The task was
diligently completed by the end of the day.
On July 15, all marked documents were transported to NSH, the designated moderation site.

34

4. IPhO2023 Website, Circulars and Registration Forms
4.1 IPhO2023 Website
The Japanese webpage of IPhO2022 (as planned at the time) was opened in 2019 for the purpose of
public relation and fundraising. The international (English) webpage of IPhO2023 was officially opened in
the autumn of 2022 and has been enriched progressively.

The pull-down menus of the IPhO2023 webpage was organized as follows:NEWS
IPhO2023
NEWSLETTERS [IPhO2023 newsletters]
GALLERY[photos and movies of IPhO2023]
FIRST CIRCULAR[pdf]
SECOND CIRCULAR[pdf]
THIRD CIRCULAR[pdf]
ORGANIZER[Organizing Committee members, Co-Organizers]
ABOUT IPhO
[linked to the IPhO Secretariat webpage https://www.ipho-new.org/]
PARTNERS[Supporters of IPhO2023]
INFORMATIONCONTEST[IPhO2023 exam questions and model answers]
Results (medals, honorary mentions, special prizes)
Experimental Exam
Theoretical Exam
COMMUNICATION
IPhO2023 Pre-Registration[Google form for pre-registration]
Request of Invitation Letter for Visa Application [Google form for invitation letter request]
IPhO2023 Team Registration[Google form for team registration]
INQUIRY BOX
FAQ*After IPhO2023, the original IPhO2023 webpage at the URL ipho2023.jp/en/ suffered from DDoS
attack, so that the webpage was relocated to international-physics-olympiad2023-tokyo.jp/

35

4.2 Pre-Announcement (Jan. 17, 2023)
On January 17, 2023, the following pre-announcement e-mail was sent to the countries/regions which
participated in at least one of the last three IPhOs --- IPhO2019 (Israel), IPhO2021 (Lithuania, online) andIPhO2022 (Switzerland, online). The e-mail addresses of the leaders of the previous years’ delegation
were taken from a list provided to us from the IPhO Headquarter. This was intended to establish the contact
channel for subsequent communication with each of the prospective participating countries/regions.
To Leaders of Countries/Regions interested in participating in IPhO2023 [sent via bcc]
I am IYE Yasuhiro, Secretary General of the Organizing Committee of IPhO2023.
This e-mail is a pre-announcement of IPhO203 in July this year. It is also intended as communication testwith the leaders of countries/regions for future communications on IPhO2023. The First Circular of IPhO2023
will be issued in about a week and will be e-mailed to each of you. The webpage of IPhO2023 ipho2023.jp/en
will be updated in due course.
If you are handing over the leadership of your country/region to someone else this year, please forward thise-mail to the new leader, and let me know his/her name and e-mail address.
Thank you for your cooperation.
Yours sincerely
Prof. IYE Yasuhiro, Secretary General, the Organizing Committee of IPhO2023

4.3 First Circular and Pre-Registration
4.3.1 First circular
The First Circular, which is reproduced on the following pages, was sent to the contact persons ofprospective participating countries/regions on January 24, 2023. At the same time the Pre-Registrationsite was opened. The representatives of those countries/regions interested in participating were asked tofill out the Pre-Registration Form.
Here, it may be worthwhile to drop a note on the web-based forms used for IPhO2023: It was anticipatedthat we would have to collect a large volume of data, at the time of full registration, including not only text
data but also different types of data such as face photos, passport photocopies, signed documents etc.
There are many kinds of web-based forms available free or at a reasonable cost. We tried a few of them.
They did not differ much in terms of function. The crucial points were; Secure data transfer and storage Capacity to handle a large volume of data Accessibility from different countries/regions
 Easy, intuitive operation for those who would fill out the form
Not knowing well about the accessibility from different regions of world, I (IYE) tentatively chose Google
form, made a beta version of Pre-Registration Form, and asked a few friends living abroad to give a try.
Confirmed positive, at least partially, the Pre-Registration Form was put into practice. Fortunately, there
seemed no problems even in countries/regions where access to internet was reputed to be strictly
controlled. Encouraged by this clearance of the first stage, I moved on to prepare the full registration form,
i.e. Team Registration Form. Here the variety of the data files and total amount of data to be collected
were the major challenge.

36

IPhO 2023 – First Circular
January 2023
Dear Colleagues,
We have the honor of hosting the 53rd International Physics Olympiad (IPhO) 2023 based on thedecision made at the International Board Meeting during IPhO2022 held online in July 2022.
IPhO2023 will take place from July 10th (Mon) to July 17th (Mon), 2023 in Tokyo, Japan. We would
like to invite you to participate in IPhO2023. Towards this important event, we are happy to sharewith you the logistic information that will help you to plan your trip.
Program: A tentative timetable of IPhO2023 is given at the end of this document to facilitate
your travel plan.
Delegations: Each participating country/region may send a delegation, normally consisting offive students (contestants) and two accompanying persons (delegation leaders) at most. The
contestants shall be students of general or technical secondary schools. Students who
have finished their school examinations in the year of the competition can be members of
the team as long as they have not commenced their university studies. The age of thecontestants should not exceed twenty years on June 30th, 2023. The delegation leaders
must be specialists in physics or physics education, capable of solving the problems of thecompetition. Each of them should be able to communicate in English. In addition to thedelegations, teams may be accompanied by observers and guests. Observers may attend
all Olympiad meetings, including the meetings of the International Board. However, they
may not vote or take part in the discussions. Guests do not attend the meetings of theInternational Board.
The promotion of gender diversity within each participating team is encouraged. Section 3 ofthe IPhO Statutes and the associated Regulations should be referred to for more details.
Hospitality: The organizer will provide and cover meals, accommodation, excursions andvarious entertainments during the Olympiad official period (10 days) starting July 9th (Sun) andending July 18th (Tue), 2023.
Transportation. Ground transportation will be provided for the official events. Transportation
service includes pick-up and drop-off of delegations* either at Tokyo International Airport (Haneda
Airport) or Narita International Airport.
* Applicable to arrivals on 8th(Sat), 9th(Sun) and early morning of 10th (Mon). Note that the Opening Ceremony starts
at 10:00 on 10th(Mon). To utilize the airport pick-up service, you have to include the flight number and arrival time in
the Full Registration Form. As for departures, airport transportation will be provided on 17th(Mon) and 18th(Tue).
Trips from and to the airport on other days have to be self-covered. Individual arrival or departure on a different
schedule than the group travel of the delegation will not be taken care of by the Organizer.

Accommodation: All students shall be staying in the dormitory within the campus of the
National Olympics Memorial Youth Center, the venue of IPhO2023. Each room is single

37

Leaders, observers and guests will be staying at the Nippon Seinenkan Hotel. The hotel rooms
are based on two people per room. If single occupancy is preferred, a surcharge has to be
incurred per night.
Travel Insurance: Each delegation is advised to take out an appropriate travel insurance policy.
Although the organizer signs up for a contingency insurance policy to cover accidents during
IPhO2023, the policy does not cover personal medical insurance.
IPhO2023 Website: The official website of IPhO2023 is https://www.ipho2023.jp/en/.
Pre-Registration: The website for pre-registration is ready. We request the representative leaderof each participating team to fill out the Pre-Registration Form at his/her earliest convenience,but no later than 15th March 2023.
This is for us to know which countries/regions are interested in participating IPhO2023, and tocollect relevant information for subsequent communication with the prospective participatingteams. Submission of this Pre-Registration Form implies neither your formal commitment to
IPhO2023, nor a formal invitation of your team to IPhO2023 by the Organizer.
The Second Circular and a Full Registration site will be available in April 2023.
Visa: Visa application may be required depending on the traveler’s origin. In case a visa isrequired, we recommend you to prepare well in advance for a visa application. Please check forthe latest information on visa issue at the following website of the Ministry of Foreign Affairs,
Japan.
https://www.mofa.go.jp/j_info/visit/visa/index.html
The Organizing Committee, upon request and registration, can provide invitation letters to assist
with the visa application.
COVID-19: It is difficult at this moment to predict the status of the COVID-19 pandemic in Japanand worldwide in July 2023. The Organizing Committee will collect and post relevant information,
while striving to prepare for the safe execution of IPhO2023. The Japanese border measuresconcerning COVID-19, as of Jan. 2023, can be found on the following webpage of the Ministry of
Health, Labour and Welfare, Japan.
https://www.mhlw.go.jp/stf/covid-19/bordercontrol.html
Participation Fee: Participation fees are set as follows:
Students:
70,000 JPY per person
Leaders:
70,000 JPY per person
Observers: 250,000 JPY per person
Guests:250,000 JPY per person
Surcharge for single room occupancy* at the Nippon Seinenkan Hotel:
12,000 JPY per night per person* Applicable only to leaders, observers and guests staying at the Nippon Seinenkan Hotel. All student rooms in the
National Olympics Memorial Youth Center are single occupancy with shared bathrooms.

Payment of the participation fees should be made by bank transfer. Details of the payment

38

method will be given in the Second Circular.
Communications:Should you have any questions, please do not hesitate to contact us at thee-mail address given below.
IPhO2023 Secretariat: e-mail address: secretariat@ipho2023.jp
We look forward to your participation, and hope that you enjoy your stay in Tokyo.
Yours sincerely,
Prof. KOBAYASHI Makoto: Chair,Prof. IYE Yasuhiro: Secretary General
The Organizing Committee of IPhO2023

39

40

4.3.2 IPhO2023 Pre-Registration Form
Upon distribution of the First Circular on Jan, 23, 2023, the following Pre-Registration site offering thefollowing Pre-Registration Form was made open.

41

Note that the sentences written in Japanese here are automatically shown in the language selected by theindividual browser.

424.4 Second Circular and Team Registration
4.4.1 Second circular
The Second Circular was sent to the contact persons of respective countries/regions and uploaded to
the IPhO2023 website on April 14, 2023.

IPhO2023
Second Circular and Call for Registration
April 2023
Dear Colleagues,
The 53rd International Physics Olympiad (IPhO2023) will be held from July 10 (Mon) to 17 (Mon), 2023 in
Tokyo, Japan. We are experiencing the pleasure of receiving pre-registration from about 90
countries/regions. Given the relatively calmed down situation of COVID-19 in Japan and elsewhere, weare happy to announce that IPhO2023 will be held as an on-site face-to-face event for the first time in four
years.
IPhO2023 Website: The official website of IPhO2023 is https://www.ipho2023.jp/en/.
Pre-Registration Status
The following 83 countries/regions have made pre-registration to IPhO2023:
Armenia
Australia
Austria,
Azerbaijan
Bangladesh
Belgium
Bolivia
Bosnia and Herzegovina
BrazilBulgaria
Cambodia
CanadaChina
Czech
Colombia
Croatia
CyprusDenmark
Egypt
El Salvador
Estonia
FinlandFranceGeorgia
Germany
GreeceHong Kong
Hungary
Iceland
India
Indonesia
Iran
IsraelItaly
Japan
Kazakhstan
Korea
KosovoKuwaitKyrgyzstan
LatviaLithuania
Luxembourg
Macao
Macedonia
Malaysia
MexicoMoldova
Mongolia
Montenegro
Nepal
Netherlands
Nigeria
NorwayPakistan
Philippines
PolandPortugal
Puerto Rico
Qatar
Romania
Saudi Arabia
SerbiaSingapore
Slovakia
Slovenia
South Africa
Spain
Suriname
SwedenSwitzerland
Syria
TaiwanTajikistan
ThailandTurkeyTurkmenistan
UkraineUnited Arab Emirates
United Kingdom United States of America
Uzbekistan
Vietnam
The following 8 countries have expressed their intention to join IPhO2023 as observer country or guest
team:
BruneiEcuador
Ghana
Honduras
Kenya
Oman
Peru
Tunisia
Team Registration Site: The Team Registration (Full Registration) site now open can be reached fromthe IPhO2023 website ipho2023.jp/en via the pull-down menu under COMMUNICATION. The password
for access to the Registration form is sent to the contact person of each team (usually the first leader).
Please complete registration at your earliest convenience, but no later than May 15 (Mon). We cannot takeresponsibility for any disadvantage or inconvenience due to delay in the team registration.

43

The Team Registration Form is somewhat lengthy, as we need to collect detailed information on each of
the participants. We appreciate your cooperation and patience in filling out the Form. After you submit theForm, you will get an acknowledging e-mail. You can change the data entries after submission, if necessary.
Prior to get started on the Team Registration Form, the following files for each participant have to beprepared and be made ready for uploading.
 Photographic portrait: clear face photo to appear on the name tag and the IPhO2023 booklet --- jpg
or gif file no heavier than 1MB.
 Pronunciation of full name: audio mp3 file no heavier than 1MB.
 Photocopy of the photo page of the passport – jpg or gif or pdf file no heavier than 1MB.
 Signed “Photography Consent Form” --- pdf file no heavier than 1MB.
 Signed “Commitment Form” –- pdf file no heavier than 1MB
The “Photography Consent Form” and the “Commitment Form” can be downloaded from the IPhO2023
webpage. Those for students and those for leaders/observers are different. They should be read
carefully, and be signed and scanned to make pdf files to be uploaded upon registration.
Participation Fee: Participation fees are set as follows:
Students:
70,000 JPY per person(Students of a “Guest Team”: 150,000 JPY per person)
Leaders:
70,000 JPY per person
Observers:
250,000 JPY per person
Guests:250,000 JPY per person
Surcharge for single room occupancy* at the Nippon Seinenkan Hotel:
12,000 JPY per night per person* Applicable only to leaders, observers and guests staying at the Nippon Seinenkan Hotel. All student
rooms in the National Olympics Memorial Youth Center are single occupancy with shared bathrooms.
Payment of the participation fees should be made by bank transfer to the following account by June 16(Fri). Remittance should be made so that the total amount of participation fees for your team is depositedin our bank account. Namely, the remittance charge should be paid by the sender.
Beneficiary:
International Physics Olympiad 2023 IPhO2023
Bank:
MUFG BANK, LTD

KAGURAZAKA BRANCH
3-7, Kagurazaka, Shinjuku-ku, Tokyo, 162-0825, Japan
Account Number: 052-0970796
SWIFT Code:BOTKJPJTXXX

If you have difficulty with bank transfer, contact us prior to the above-mentioned deadline so that we candiscuss on the payment method.
If you are unable to make bank transfer despite all your efforts, we accept payment in cash at theregistration desk of IPhO2023. You have to bring the exact total amount of the participation fees of yourteam in JPY.
Cancellation or any other schedule changes must be notified to the IPhO2023 organizer by June 30 (Fri).
Cancellation after this date will not be refundable.

44

Hospitality: In accord with the tradition of IPhO, we extend our hospitality. We will provide and coveraccommodation of the registered participants during the Olympiad official period (10 days) beginning in
the evening of July 9 (Sun) and ending in the morning of July 18 (Tue) 2023.
Service of meals starts with a get-together party in the evening of July 9 (Sun) and ends with a farewelllunch on July 17(Mon).
Excursions and entertainments during IPhO2023 will be covered by the organizer.
Transportation. Ground transportation will be provided for the official events. Transportation service
includes pick-up and drop-off of delegations* either at Tokyo International Airport (Haneda Airport) or
Narita International Airport.
* Applicable to arrivals on 8 (Sat), 9 (Sun) and early morning of 10 (Mon). Note that the Opening Ceremony starts at
10:00 on 10 (Mon). Arrival in the morning of the same day is not advisable, considering the time for immigration
procedures and transportation from the airport. To utilize the airport pick-up service, you have to include the flightnumber and arrival time in the Team Registration Form. As for departures, airport transportation will be provided on
17 (Mon) and 18 (Tue).
Trips from and to the airport on other days have to be self-covered. Individual arrival or departure on a different
schedule than the group travel of the delegation will not be taken care of by the Organizer.

Accommodation: All students shall be staying in the dormitory within the campus of the National
Olympics Memorial Youth Center, the venue of IPhO2023. Each room is single occupancy. Several rooms
constitute a unit with a shared bathroom.
Leaders, observers and guests will be staying at the Nippon Seinenkan Hotel. The hotel rooms are basedon two people per room. If single occupancy is preferred, a surcharge per night has to be paid.
Travel Insurance: Each delegation is advised to take out an appropriate travel insurance policy.
Although the organizer signs up for a contingency insurance policy to cover accidents during IPhO2023,
the policy does not cover personal medical insurance.
Visa: Visa application may be required depending on the traveler’s origin. In case a visa is required, werecommend you to prepare well in advance for a visa application. Please check for the latest information
on visa issue at the following website of the Ministry of Foreign Affairs, Japan.
https://www.mofa.go.jp/j_info/visit/visa/index.html
The Organizing Committee, upon request and registration, can provide invitation letters to assist with thevisa application. Visit the “Request for Letter of Invitation to IPhO2023” page via the pull-down menu under
CORRESPONDENCE menu, and fill out the Form.
COVID-19: It is difficult at this moment to predict the status of the COVID-19 pandemic in Japan andworldwide in July 2023. The Organizing Committee will collect and post relevant information, while striving
to prepare for the safe execution of IPhO2023. The Japanese border measures concerning COVID-19, as
of April 2023, can be found on the following webpage of the Ministry of Health, Labour and Welfare, Japan.
https://www.mhlw.go.jp/stf/covid-19/bordercontrol.html
Exam Tools: We are using the OlyExam Tool, first introduced in IPhO2016, for discussions, voting,translating, marking and managing exams. Access to the OlyExam system will be via a WiFi network.
Leaders and observers are advised to bring their own personal computers which they are used to. Make
sure to bring your international power adaptor. Limited number of rental computers will be available forthose teams experiencing troubles with their computers. Please be reminded that the electrical power
outlet in Japan is “type A” supplying 100V a.c. at 50Hz (in the eastern part of Japan including Tokyo).
Calculators: All contestants will use CASIO fx-82cw calculator to be provided by the organizer. CASIO

45

company provides a web-based emulator of the calculator with which students can practice the usage ofthe calculator in advance. The access code will be sent to the contact person (usually the first team leader)of the country/region after he/she has completed the Team Registration.
Distribution of Experimental Kits: To each participating country/region, we will present one set of theexperimental kit used in the exam. If you want more, you can purchase either brand new kits at a priceof 80,000 JPY/set which is an actual cost, or used kits at a much reduced price. The exact price of usedkits cannot be predetermined because it should depend on their condition after use. The number of setsthat can be purchased is subject to the availability.
Excursions:<For Students>
Half-day excursions within the city of Tokyo will take place on July 12 (Wed) and July 14 (Fri).
A1. Yokohama
A2. Asakusa and Ueno
A3. Odaiba
One-day excursions in Kanto (greater metropolitan) area will take place on July 15 (Sat.) and July 16(Sun.).
B1. Hakone
B2. Tsukuba
B3. Nikko
B4. Kamakura
Description of the excursion courses can be found in the Excursion Guide attached to the Second
Circular.
Note that the choices of excursion courses should be made on a team base. Namely, all students of ateam must go together with an attending student supporter. There should be no going off on one’s own.
The organizer will arrange the schedule of excursions so as to meet the choices as much as possible.
<For Leaders and Observers>
Half-day excursions within the city of Tokyo for leaders and observers will take place on July 11 (Tue)and on July 13 (Thur), while students are sitting for the exams. The destination will be “Asakusa andUeno” and “Odaiba and Fukagawa“.
Communications:Should you have any questions, please do not hesitate to contact us via the
INQUIRY FORM activated from the pull-down menu under the COMMUNICATION item in the menu-bar.
We look forward to meeting you in Tokyo in July.

The Organizing Committee of IPhO2023

46

4.4.2 Photography consent form and commitment form
Photography consent forms and commitment forms to be signed by the students (contestants), andthose for the escorting adult participants (leaders and observers).

IPhO2023 – Photography Consent Form (Student)
Student:
Full Name _________________________________
Postal address __________________________________________________________Country/Region _____________________
During my participation in the 53rd International Physics Olympiad (IPhO2023) taking place in July 2023, I
understand that my picture and/or voice may be recorded by any means of photography, audio/video
recording, etc.
I am aware and agree that those recordings might be used to promote the IPhO2023 (internet, newspapers,
radio, television, social media, etc.) and/or for administrative purposes including but not limited to fraud
prevention. No material will be used outside the scope of IPhO2023.
I hereby grant the IPhO2023 organizer the right to use the mentioned pictures and audio/video records for
public relations strictly related to the IPhO2023 and renounce any interest derived from the use of thatmaterial, such as royalties, proceeds or other benefits.
By signing this form below, I agree to the aforementioned rules. If I disagree, I send an e-mail tosecretariat@ipho2023.jp by June 30th, 2023 with the title “IPhO2023 photography consent [Country]”, toexplicitly state where the consent is not given.
Date
Signature*If the above signer is underage under the law of the country, legally responsible person:
Full Name in print

Signature47

IPhO2023 – Commitment Form (Student)
As a proud IPhO2023 contestant,

I certify that I am aware of the rules of IPhO contest, in particular that all devices with
communication function (cellphones, connected watches, etc.) have to be deposited with theorganizer until the completion of experimental and theoretical examinations.



I commit myself to work on the examinations with full integrity, not to cheat or attempt to during
the examinations, and not to get in touch with any external contact during or before theexaminations.



I understand that any case of cheating (or attempt) might lead to my disqualification from
IPhO2023 and that any case of cheating (or attempt) might lead to the elimination of my entire
team.



I respect the spirit and ideals stated in the IPhO Statutes. I cooperate with the IPhO2023 organizer
to maintain a friendly atmosphere throughout the IPhO2023. I refrain from any political messages
or actions.

[Excerpt from the Section 2 of the IPhO Statutes]
The competition is conducted in the friendly atmosphere designed to promote future collaborations and to encourage the formation offriendship in the scientific community. Therefore all possible political tensions between the participants should not be reflected in any
activity during the competition. Any political activity directed against any individuals or countries is strictly prohibited.



I commit myself to cooperate with the IPhO2023 organizer for a safe execution of the event. I
obey the Japanese laws* and the usage rules of the National Olympics Memorial Youth Center.
I follow directions of the IPhO2023 organizer with regards to the COVID-19 infection prevention
and emergency safety measures against natural disasters such as earthquake.

*Be advised of Japanese laws and regulations: Drag control is extremely strict. Alcohol and/or tobacco are prohibited under 20,
although the adult age is 18.

Date
Full Name in print

Signature48

IPhO2023 – Photography Consent Form (Leader/Observer)
Participant (leader/observer):Full Name _________________________________
Postal address __________________________________________________________Country/Region _____________________
During my participation in the 53rd International Physics Olympiad (IPhO2023) taking place in July 2023,
I understand that my picture and/or voice may be recorded by any means of photography, audio/video
recording, etc.
I am aware and agree that those recordings might be used to promote the IPhO2023 (internet,
newspapers, radio, television, social media, etc.) and/or for administrative purposes including but notlimited to fraud prevention. No material will be used outside the scope of IPhO2023.
I hereby grant the IPhO2023 organizer the right to use the mentioned pictures and audio/video records
for public relations strictly related to the IPhO2023 and renounce any interest derived from the use ofthat material, such as royalties, proceeds or other benefits.
By signing this form below, I agree to the aforementioned rules. If I disagree, I send an e-mail tosecretariat@ipho2023.jp by June 30th, 2023 with the title “IPhO2023 photography consent [Country]”,
to explicitly state where the consent is not given.

Date
Signature49

IPhO2023 – Commitment Form (Leader/Observer)
As a IPhO2023 participant (leader/observer),

I cooperate with the IPhO2023 organizer for a fair execution of the contest. In particular, intranslating the exam problems, I exercise my meticulous attention to exclude any kinds ofhints that are not present in the original problem description.

I understand that any case of misconduct (or attempt) might lead to the elimination of myentire team from IPhO2023.

I respect the spirit and ideals stated in the IPhO Statutes. I cooperate with the IPhO2023
organizer to maintain a friendly atmosphere throughout the IPhO2023. I refrain from any politicalmessages or actions.

[Excerpt from the Section 2 of the IPhO Statutes]
The competition is conducted in the friendly atmosphere designed to promote future collaborations and to encourage the formationof friendship in the scientific community. Therefore all possible political tensions between the participants should not be reflected inany activity during the competition. Any political activity directed against any individuals or countries is strictly prohibited.



I understand that the above-mentioned “prohibition of political activity directed against any
individuals or countries” does not preclude sound and constructive discussions on the proposed
amendments to the IPhO Statutes and Regulations, to be put on the agenda in the final sessionof the International Board Meeting (IBM) in IPhO2023.

I commit myself to cooperate with the IPhO2023 organizer for a safe execution of the event. I
obey the Japanese laws* and the usage rules of the National Olympics Memorial Youth Center.
I follow directions of the IPhO2023 organizer with regards to the COVID-19 infection prevention
and emergency safety measures against natural disasters such as earthquake.

*Be aware of Japanese laws and regulations: Drag control is extremely strict. Alcohol and/or tobacco are prohibited under 20,
although the adult age is 18.

Date
Full Name in print

Signature50

4.4.3 Flow chart of the team registration form
The followings are the flow charts of the Team Registration Form for different categories of participatingteams.

51

52

53

4.4.4 Team registration form
Shown below are some pages ofis the Team Registration Form which the contact person of eachparticipating delegation was requested to fill out by May 15.

54

55

56

57

58

59

60

4.5 Third Circular
The Third Circular was distributed on June 30.

IPhO2023 Third CircularJune 30, 2023
Dear Colleagues,
The 53rd International Physics Olympiad (IPhO2023) to be held from July 10 (Mon) to 17 (Mon), 2023 in
Tokyo, Japan is only 10 days away. We trust your team members are busy in preparation forparticipation in IPhO2023. Here we give you a few last minutes announcements and some tips for travel
to Tokyo.
IPhO2023 Website: The official website of IPhO2023 is https://www.ipho2023.jp/en/.
Participating Countries and Regions
We expect the following teams enter the IPhO2023 contest:
Armenia
Australia
Austria,
Azerbaijan
Bangladesh
Belgium
Bolivia
Bosnia and Herzegovina
BrazilBulgaria
Cambodia
CanadaChina
Colombia
Croatia
Cyprus
Czech
Denmark
El Salvador
Estonia
FinlandFranceGeorgia
Germany
GreeceHong Kong
Hungary
Iceland
India
Indonesia
Iran
IsraelItaly
Japan
Kazakhstan Korea
KosovoKyrgyzstan
LatviaLithuania
Luxembourg
Macao
Macedonia
Malaysia
MexicoMoldova
Mongolia
Montenegro
Nepal
Netherlands Nigeria
NorwayPakistan
Philippines
PolandPortugal
Puerto Rico
Qatar
Romania
Saudi Arabia Serbia
Singapore
Slovakia
Slovenia
South Africa Spain
Suriname
SwedenSwitzerland
Syria
TaiwanTajikistan
ThailandTurkeyTurkmenistan Ukraine
United Arab Emirates
United Kingdom
United States Uzbekistan
VietnamOly team of Individuals
The followings are guest teams and observer countries:
Honduras
Kenya
KuwaitOman

Tunisia[IMPORTANT] Visit Japan Web
To facilitate the procedures at the Immigration Control and Custom, please visit the “Visit Japan Web”
and make registration prior to your trip to Japan.
https://www.digital.go.jp/en/services/visit_japan_web-en/[IMPORTANT] Travel insurance
Each delegation is advised to take out an appropriate travel insurance policy. Although the organizer
signs up for a contingency insurance policy to cover accidents during IPhO2023, the policy does not coverpersonal medical insurance.
Travel and Airport Pickup
Many teams have notified us of their travel itinerary. If you have yet to do so, please fill out the “Notificationof Team Itinerary Form” from https://forms.gle/Qfha5QYbUheVbg419 at your earliest convenience. We
arrange for transportation between the airport (either Haneda or Narita) and the venue of IPhO2023.
For those who travel by themselves, the address and access information are given below.
<The National Olympics Memorial Youth Center>61

3-1, Yoyogi Kamizono-cho, Shibuya-ku, Tokyo 151-0052
Accessc Guide: https://nyc.niye.go.jp/wp/en/access-train/<Nippon Seinenkan Hotel>
4-1 Kasumigaoka-machi, Shinjuku-ku, Tokyo 160-0013, Japan
Access Guide: https://nippon-seinenkan.or.jp/en/access.php
Registration Desk at the National Olympics Memorial Youth Center
The charted bus from the airport brings all team members to the NYC, where you are to complete
registration, get your nametag, a IPhO2023 handbook, and a set of IPhO2023 goods (a cap, a T-shirt, abag). For the students an insulated water bottle will be provided.
Students (contestants) have to deposit all their electronic devices with communication capability, mobile
phones, personal computers, tablets, smart watches. Failure to comply with this rule may result in
disqualification of the entire team. Those electronic devices will be handed back after completion of thetheory exam on Thursday.
Those teams who have chosen to pay the participation fee in cash can do so here. We may ask you
about the difference between the invoice and the amount of remittance.
There will be a Get Together from 17:00 on July 9 where light meal and beverage will be served. Afterthe Get Together, the adult participants will be transported to the Nippon Seinenka Hotel by charteredbuses.
Stay at the National Olympics Memorial Youth Center (Students)
All students are accommodated in Building A of the National Olympics Memorial Youth Center (NYC),
the venue of IPhO2023. Each room is single occupancy. Several rooms constitute a unit with a sharedbathroom.
There are no supply of amenities in the NYC except shampoo and soap in the bathroom. Do bring yourown towels, tooth brushes, tooth paste, etc.
Because the NYC is surrounded by greens, you may be annoyed by mosquitos and other insects. You
may want to bring insect repellant and anti-itch ointment, although the organizer also prepares some.
There are coin-operated washing machines and dryers. You may want to bring detergent you are familiar
with, although you can buy detergent in the shop.
A nurse station will be set up within the NYC for emergency medical response. Standard stock medicationand medical treatment will be provided, but oral medicine will not be prescribed. Therefore, those who
suffer from chronic ailment and/or carry risk of disease should make sure to bring their own medication.
In this connection, be warned that the control of narcotic drug is extremely strict in Japan.
Stay at the Nippon Seinenkan Hotel (Adult Participants)
Adult participants (leaders, observers and guests) will stay at the Nippon Seinenkan Hotel unlessarranged otherwise by themselves. We do our best to meet your request for room assignment, but
depending on the availability, we may ask you for some adjustments, Standard hotel amenity supplies
such as towels, toothbrushes, razors will be provided. Any extra payments, such as room service, laundry,
contents of refrigerator, charged to your room has to be paid individually upon check-out.
[IMPORTANT] Extra Nights Stay
We have found that significant number of teams need accommodation for nights before July 9 and/or
those after Jul 17. To meet such needs, we have secured rooms in the NYC, arrange the accommodation
as follows:<Early Arrivals>
Those teams who comes to Japan on July 8 (or July 7) will be accommodated in the NYC. On July 9, theadult participants move to the Nippon Seinenkan Hotel.
<Late Departures>
We ask all adult participants to check out the Nippon Seinenkan Hotel in the morning of July 17 (Mon)and go to the Closing Ceremony at the NYC. Those who stay for the night of July 17 (and possibly for thenight of July 18 also) will be accommodated in the NYC. Any adjustment of room charges (i.e. surcharges

62for single occupancy) associated with this arrangement will be settled at the Registration Desk. We
apologize for inconvenience and appreciate your kind understanding.
As stated in the preceding page, there are no supply of amenities in the NYC, except shampoo and soap
in the bathroom. So bring your own towels, tooth brushes, tooth paste, etc, if you are going to stay somenights in the NYC. .
Miscellaneous
There is no dress code in IPhO2023. Tokyo in mid July is generally hot and humid. The daytime
temperature can be anywhere between 30 to 35 Celsius. The rainy season may or may not be over by
mid July, so there is a chance of occasional rain.
Some may feel freezing in some of the air-conditioned rooms. It is advisable to bring something to wear
in order to adjust to the room temperature.
Bring a pair of comfortable shoes for excursions and other activities. Those who suffer motion sickness
should bring an appropriate medication, especially for the one-day excursions with long bus ride.
You are recommended to bring a folding umbrella or a compact rain wear in preparation of occasionalrain
The electricity in Japan is 100 volts and 50 Hz (in Tokyo area). The power plug sockets are type A. Make
sure to bring a suitable power adapter.
Tap water in Japan is safe to drink. Coin-operated beverage vender machines are everywhere.
COVID-19
Since May, the COVID-19 has been down-categorized as common infectious disease. Accordingly, there
is no special border measures concerning COVID-19. Infection prevention measures such as wearing ofa mask are left to the individual personal discretion.
Still, we have to exercise due precaution to prevent infections. The organizer will prepare antibody test
kits in stock for quick check. If you notice changes in your physical condition, do notify the staff of
IPhO2023 organizer and visit nurse station.
International Board Meeting
The International Board Meetings will be held in the meeting rooms on the 8th floor of the Nippon
Seinenkan Hotel. The main meeting room (Room Yellow) is for leaders only. Observers can watch themonitor screen in another meeting room (Room Blue), or on-line broadcast from the hotel rooms. In thelatter case, the TV set in the hotel room can be used as external display for your PC. If you want to utilizeit, bring an HDMI cable.
The OlyExams Tool will be used for discussions, voting, translating, marking and managing exams. We
trust the leaders are already familiarized with the operation of the OlyExams Tool by doing the trial workof translating the General Instructions.
Access to the OlyExams system will be via a WiFi network. Leaders and observers are expected to bring
their own personal computers. Make sure to bring your international power adaptor. The power outlet in
the meeting room is 100 volts and the power plug socket is type A.
Calculators
All contestants will use CASIO fx-82cw calculator to be provided by the organizer. CASIO company
provides a web-based emulator of the calculator with which students can practice the usage of thecalculator in advance. The access codes have been sent to the leaders of the participating
countries/regions. We trust the contestants had chance to practice the usage. In the afternoon of July 10(Mon), there will be a session where usage of the CASIO calculator fx-82cw will be explained, andstudents can give hands-on practices.

63

Distribution of Experimental Kits
To each participating country/region, we will present one set of the experimental kit used in the exam. If
you want more, you can purchase either brand new kits at a price of 80,000 JPY/set which is an actual
cost, or used kits at a much reduced price. The exact price of used kits cannot be predetermined because
it should depend on their condition after use. The number of sets that can be purchased is subject to theavailability.
Excursions<For Students>
Half-day excursions within the city of Tokyo will take place on July 12 (Wed) and July 14 (Fri).
A1. Yokohama
A2. Asakusa and Ueno
A3. Odaiba
One-day excursions in Kanto (greater metropolitan) area will take place on July 15 (Sat.) and July 16(Sun.).
B1. Hakone
B2. Tsukuba
B3. Nikko
B4. Kamakura
Description of the excursion courses can be found in the Excursion Guide attached to the Second
Circular. Note that the choices of excursion courses should be made on a team base. Namely, allstudents of a team must go together with an attending student supporter. There should be no going off
on one’s own.
<For Adult Participants>
Half-day excursions within the city of Tokyo for leaders, observers and guests will take place on July 11(Tue) and on July 13 (Thu), while students are sitting for the exams. The destination will be “Asakusa
and Ueno” and “Odaiba and Toyosu (fish market)“.

Safe trip to Japan. We look forward to welcoming you in Tokyo.
The Organizing Committee of IPhO2023

64

65

66

4.6 Request form of invitation letter for visa application
We issued upon request a letter of invitation to IPhO2023 to those who needed visa to enter Japan. The
following is the Google form for the request of invitation letter.

67

5. IPhO2023 Contest Results
5.1 Participating Countries and Regions
Regular Participation (80)Armenia
Australia
Austria,
Azerbaijan
Belgium
Bolivia
Bosnia and Herzegovina
Bulgaria
Cambodia
CanadaChina
Croatia
Cyprus
Czech
Denmark
Estonia
FinlandFranceGeorgia
GreeceHong Kong
Hungary
IcelandIndonesia
Iran
IsraelItaly
Kazakhstan
Korea
KosovoKyrgyzstan
Lithuania
Luxembourg
Macao
Macedonia
MexicoMoldova
Mongolia
Montenegro
Netherlands
NorwayPakistan
Philippines
Portugal
Puerto Rico
Qatar
Romania
SerbiaSingapore
Slovakia
Slovenia
Spain
Suriname
SwedenSwitzerland
TaiwanTajikistan
ThailandTurkeyUkraineUnited Arab Emirates
United Kingdom
United States
Uzbekistan
Vietnam
Team of Individuals (1)Oly Team
Guest Team (1)Kenya
Observer Countries (2)KuwaitOman

Bangladesh
BrazilColombia
El Salvador
Germany
India
Japan
LatviaMalaysia
Nepal
PolandSaudi Arabia
South Africa
Syria
Turkmenistan

5.2 Participants (contestants, leaders, observers and guests)*Figures in parentheses are number of females.
Contestants (Students)
Regular Contestants
Guest Students
Sub Total

388 (43)4 (1)392 (44)

Adult Participants
Leaders
Observers
GuestsSub Total

155 (13)96 (19)17 (9)
268 (41)

Grand Total

660 (85)68

5.3 Contest Results and Awards
5.3.1

Medals and honorable mentions69

— Gold Medals —–Last NameFirst NameCountry/Region Exp.
YU
Bowen
China
15.6
DING
Zhuoli
China
15
TIAN
Xiangchen
China
14.9
ZHAO
Hanhong
China
14.1
FAN
CollinUnited States
16
JIANG
Daibing
China
12.3
MOMOIU
Alexandru
Romania
13.2
LEE
Junsuh
Korea
11.9
HAN
Jongyoon
Korea
11.1
BOBKOV
Viacheslav
OLY team
13.7
CHANG
Ya-Cheng
Taiwan
13.4
LEE
Hyunchae
Korea
10.3
KIM
Evan
nited States
10.8
YEVTUSHENKO Feodor
United States
10.1
OROS
Vlad-Stefan
Romania
11.9
SHI
Zian
United States
11.1
NOH
Ian
Korea
10.4
SUH
Kyumin
Korea
11
BURTSEVRoman
OLY team
13.9
BACIAK
Filip
Poland
10.9
DRAGOMIR
Andrei-Darius
Romania
10.3
CHANG
Cheng-Kuang
Taiwan14.2
NGUYEN
Tuan Phong
Vietnam
9.3
DOLIA
Vsevolod
OLY team
10.2
BORAD
Mehul
India
11.1
TANAKA
Yuki
Japan
10.3
PHADETSUWANNUKUN Nutdech Thailand
11.5
ADITYA
India
8
IMAMURA
Kotaro
Japan
10.8
WANG
Zhao-Guo
Taiwan
11.4
LAM
Chung Wang
Hong Kong
11.9
ANDOLŠEK
Peter
Slovenia
14.4
ERSHOV
Aleksandr
OLY team
8.5
VOHoang Hai
Vietnam
8.4
POTAPOVEgor
OLY team
12
SHAH
Dhruv
India
8.9
AKDAĞ
Emir
Turkey7.6

Theory Total
29.6
45.2
29.8
44.8
29.9
44.8
30
44.1
26.2
42.2
29.7
42
28
41.2
29.1
41
29.9
41
27.1
40.8
27.4
40.8
29.9
40.2
29.3
40.1
30
40.1
27.7
39.6
28.4
39.5
28.8
39.2
28.1
39.1
25.2
39.1
27
37.9
27.5
37.8
23.3
37.5
28.2
37.5
27.2
37.4
25.5
36.6
26.3
36.6
25.1
36.6
28.5
36.5
25.5
36.3
24.9
36.3
24.3
36.2
21.8
36.2
27.4
35.9
27.5
35.9
23.8
35.8
26.8
35.7
28
35.6

Medal
Gold
Gold
Gold
Gold
Gold
Gold
Gold
Gold
Gold
Gold
Gold
Gold
Gold
Gold
Gold
Gold
Gold
Gold
Gold
Gold
Gold
Gold
Gold
Gold
Gold
Gold
Gold
Gold
Gold
Gold
Gold
Gold
Gold
Gold
Gold
Gold
Gold

Theory Total
27.5
35.55
27
35.3
26.7
34.9
25.7
34.8
26.1
34.7
24.9
34.4
27.2
34.4
26.6
34.2
26
34.1
23.5
33.2
28.8
33
23.9
32.8
22
32.5
24.4
32.4
28.1
32.3
23.5
32.3
22.6
32.1
22.5
32
22.3
31.9

Medal
SilverSilverSilverSilverSilverSilverSilverSilverSilverSilverSilverSilverSilverSilverSilverSilverSilverSilverSilver— Silver Medals —Last Name
HSU
RAM
CHEN
PITEBAY
IWASHITALIU
CHEN
TUDOSEGOYALDI GRAZIAKITAJINDALMYLET
BISSIMBI
KEDIA
MOOSAVINURSAGATOVZHUHUIFirst Name
Zi-Siang
Ido
Peng-Wei
Yersultan
Koki
Lincoln
ShuoyanRares Felix
Raghav
Guglielmo
Shunsuke
ShanayAlexander
Doszhan
RhythmMohammadMargulan
Coy
Pok ShingCountry/Region Exp.
Taiwan8.05
Israel8.3
Taiwan8.2
Kazakhstan
9.1
Japan
8.6
Hong Kong
9.5
United States
7.2
Romania
7.6
India
8.1
Italy
9.7
Japan
4.2
Singapore
8.9
United Kingdom 10.5
Kazakhstan
8
India
4.2
Iran
8.8
Kazakhstan
9.5
United Kingdom 9.5
Hong Kong
9.6

70

TAN
Pin CheSingapore
8.4
ZAZUBYK
Diana
Ukraine
6.4
GULATI
Ojas
United Kingdom 6.9
NGUYEN
Tuan Duong
Vietnam
5.8
WEINMAN
Matan
Israel
7.6
SHIRINBAYAN
Mahdi
Iran
7.1
KAHU
Kristjan-Eerik
Estonia
7.8
KWOK
Ching Yeung
Hong Kong
9.8MAROŃ Andrzej Franciszek
Poland
9.4
WALACH
Doron
Israel8.1
YERKEBAYEVAlisher
Kazakhstan
6.8
KARAN
Val
Croatia
5.3
HE
Jingyang, James Singapore
8.3
LIPIEC
Michał Piotr
Poland
8.5
UGULAVA
IrakliGeorgia
8SUN
Yu Chieh
Singapore
5.4
KARPIEJCZYKStanisław Marcin Poland
9
ARÉVALO AGUIRRE Sebastián Andrés El Salvador 7.5
LI
YichenSingapore
8.6
DOS SANTOS SILVA Paulo Henrique
Brazil
4.5
BABELIS
Tomas
Lithuania
10.8
GAYDUKOV
Alexander
Slovenia
9.1
MIRICA
Ioan-Alexandru
Romania
4.2
HIGASHIGAWA Leon
Japan
8.2
NITZAN
Omri
Israel
7.8
JOSHI
DouglasAustralia
6.9
CHAN
KelvinAustralia
8.5
LE
Viet Hoang Anh Vietnam
5.2
GHANBARI
Ali
Iran
3.6
ROSIAR
SamuelCzech
6.3
CHANKASAMSAT Thanassorn
Thailand
2.7
UN
Chong Un
Macao
6
FUNATA
Fansen Candra
Indonesia
7.5
FATHI
Sina
Iran
4.4
DE ANDRADE PORFÍRIO Murilo Brazil
9.7
VORONA
Victor
Moldova
7.1DŽAVORONOK Adam
Slovakia
6.3
PATTARAPON
Punlertrapee
Thailand
5.7
DERE
Kaan
Turkey5.9
FAUCHEU
HannahFrance
7.7
OTGOCHULUU Anirchuluu
Mongolia
7.5
NÜSKE
Anton
Germany
9.3
ROUAN
Mathurin
France5.1
SADIKHZADA
Sadig
Azerbaijan
5.5
TCHOTASHVILI Dachi
Georgia
8.6
WALD
Inbar
Israel
4.2
LBATH
MounirFrance
6.1
STORBACKA
MelvinSweden10.9
GONZALEZ FILIPOV Daniel
Switzerland
8.1
CHANDRA
Savero Lukianto Indonesia
4.7
ONG
Zhi Zheng
Malaysia
10.4
RYD
Emil
Sweden6.6
KARAPETYAN
HovsepArmenia7İŞKESEN
Mehmet Anıl
Turkey8.3
TRABZON
Ahmet Bahadır
Turkey
5.7

23.4
25.4
24.8
25.8
23.7
24
22.8
20.7
21.1
22.2
23.5
24.9
21.8
21.4
21.8
24.3
20.3
21.7
20.2
24.1
17.7
19.2
24
19.9
20.2
21
19.1
22.2
23.6
20.7
24.3
20.9
19.3
22.3
16.8
18.9
19.7
20.3
20.1
18.2
18.4
16.4
20.6
20.1
17
21.4
19.3
14.4
17.1
20.5
14.8
18.6
17.9
16.9
19.5

31.8
31.8
31.7
31.6
31.3
31.1
30.6
30.5
30.5
30.3
30.3
30.2
30.1
29.9
29.8
29.7
29.3
29.2
28.8
28.6
28.5
28.3
28.2
28.1
28
27.9
27.6
27.4
27.2
27
27
26.9
26.8
26.7
26.5
26
26
26
26
25.9
25.9
25.7
25.7
25.6
25.6
25.6
25.4
25.3
25.2
25.2
25.2
25.2
25.2
25.2
25.2

SilverSilverSilverSilverSilverSilverSilverSilverSilverSilverSilverSilverSilverSilverSilverSilverSilverSilverSilverSilverSilverSilverSilverSilverSilverSilverSilverSilverSilverSilverSilverSilverSilverSilverSilverSilverSilverSilverSilverSilverSilverSilverSilverSilverSilverSilverSilverSilverSilverSilverSilverSilverSilverSilverSilver

Theory
17.7
14.9
17.6
16.6
18.9

Total
25
24.9
24.7
24.5
24.3

Medal
BronzeBronzeBronzeBronzeBronze— Bronze Medals —Last NameWONGTEKRIWAL
CHANG
PHAN
SULTANOVFirst NameCountry/Region
Connor Tianzheng Canada
AdityaUnited Kingdom
Kia Yau
Malaysia
The Manh
VietnamJavohir
Uzbekistan

Exp.
7.3
10
7.1
7.9
5.4

71

GEORGIEVSKI Majkl
Macedonia
CHUA
Harold Scott
Philippines
ISHTIAK
Golam
Bulgaria
LUKIANIKHIN
Viktor
UkraineECKSTÄDT
OliverGermany
LEINONEN
Eppu
FinlandLI
ZanderCanadaPERKOVIĆ
Borna
Croatia
SODSRI
Nopparuj
Thailand
ISMOLDAYEV
Margulan
Bulgaria
ZHANG
Wenhe
CanadaAMBROŽIČ
Žan
Slovenia
TVALAVADZE
LukaGeorgia
ROHNER
MoritzLuxembourg
KREJAN
Samo
Slovenia
JELESIJEVIĆ
TadijaSerbiaCHEN
LiamAustralia
JAVORA
Lukáš
Czech
SCHOMERUS
Arved
Denmark
FEY
Dávid
Hungary
HIP
Vuk
SerbiaMOLNÁR-SZABÓ Vilmos
Hungary
SKIPPER
Timothy DavidSpain
GANBOLD
Azjargal
Mongolia
BRVAR
Miha
Slovenia
SERRANO CAPATINA Adrian
Switzerland
BARSEGHYAN Areg
Armenia
MANJAVIDZE
AndriaGeorgia
WONG
Jian Bin
Malaysia
YOVCHEV
Yovo
Bulgaria
ABRAR
MD Fahim
Bangladesh
TAVARES VITORIANO Lucas
BrazilTSUTSUI
Kodai
SwitzerlandKAMIŃSKI
Mateusz
PolandDIMITROV
Rumen Lyubomirov Bulgaria
FEYZ
ShayanIran
NURTAY EV
Dair
Kazakhstan
STOJANOVSKI Jan
Macedonia
KÖHLER
Luise
Germany
PAABO
Ralf Robert
EstoniaÜNVER
Arda
TurkeyPOSPIECH
Luke
Germany
ISMAIL Muhammad Arif Khalfani Indonesia
SUVOROVPetro
UkraineGURBAZAR
Batbayar
Mongolia
ARAKELYAN
Maria
Armenia
SHAO Eric Yuang
CanadaKONDRACHUK Yaroslav
Ukraine
AGHAYAN
Arsen
Armenia
VOGEL
ChristianGermany
BOHDAN
MarynaUkraineTODOROVIĆ
Sava
SerbiaABDULKARIM
Murad
Azerbaijan
BENCZ
Benedek
HungaryMOLNÁR
Barnabás
Hungary
RUSU
PaisieMoldova
GECHEV
Bayan
Bulgaria
KWOK
Tsz YinHong Kong
ABBASOV
Nijat
Azerbaijan
MATHE
JulianBelgium
RISTIĆ
Tadej
SerbiaMIDŽIĆ
DženanBosnia and Herzegovina
CHU
Wai InMacaoPÕLDMAA
SaskiaEstonia
JONGMAN-RIOS Mali
United Kingdom

7.3
5.1
6.4
4.5
6.8
5.5
8
5.9
4.5
5.7
4.5
11.9
5.4
9.6
8.8
4.3
7.9
3.2
6.1
5.2
2.8
6.9
5.5
4.1
9.1
8.9
5.2
5
7.9
6.1
3.6
3.9
6
6.4
5
3.1
5
5.7
7.2
7.1
4.5
9.2
4.1
5
2.7
2.2
5.2
4.9
3.7
5.4
3.1
4.1
5.5
3.6
6.5
6.5
4.3
4.1
2.3
3.6
3.9
4.2
8.5
5.9
7.3

16.9
19.1
17.6
19.5
16.9
18.1
15.5
17.6
18.6
17.3
18.5
11
17.2
12.9
13.7
18.1
14.3
19
16.1
17
19.4
15.2
16.5
17.8
12.8
12.9
16.4
16.5
13.6
15.2
17.6
17.1
15
14.6
15.9
17.7
15.8
15
13.4
13.5
16
11.1
16.1
15.2
17.4
17.7
14.6
14.7
15.8
14.1
16.3
15.2
13.7
15.5
12.3
12.3
14.4
14.6
16.3
15
14.7
14.3
10
12.5
11.1

24.2
24.2
24
24
23.7
23.6
23.5
23.5
23.1
23
23
22.9
22.6
22.5
22.5
22.4
22.2
22.2
22.2
22.2
22.2
22.1
22
21.9
21.9
21.8
21.6
21.5
21.5
21.3
21.2
21
21
21
20.9
20.8
20.8
20.7
20.6
20.6
20.5
20.3
20.2
20.2
20.1
19.9
19.8
19.6
19.5
19.5
19.4
19.3
19.2
19.1
18.8
18.8
18.7
18.7
18.6
18.6
18.6
18.5
18.5
18.4
18.4

BronzeBronzeBronzeBronzeBronzeBronzeBronzeBronzeBronzeBronzeBronzeBronzeBronzeBronzeBronzeBronzeBronzeBronzeBronzeBronzeBronzeBronzeBronzeBronzeBronzeBronzeBronzeBronzeBronzeBronzeBronzeBronzeBronzeBronzeBronzeBronzeBronzeBronzeBronzeBronzeBronzeBronzeBronzeBronzeBronzeBronzeBronzeBronzeBronzeBronzeBronzeBronzeBronzeBronzeBronzeBronzeBronzeBronzeBronzeBronzeBronzeBronzeBronzeBronzeBronze72

REUTIN
Ilya
Latvia6.5
KOTZAMPASIS Odysseas
Greece
6.1
COSENTINO
GiulioItaly
5.4
DUBROVSKISStanislavs
Latvia
6.9
QADAH
Hussain Jamal H Saudi Arabia
2.3
NIKOLAOU
Charalampos
Greece
3.4
PETROSYAN
Vyacheslav
Armenia
2.5
FARES MENHEM Hugo
Brazil
5.1
LECLERC
AdelineFrance
4.7
VUKOVIĆ
ViktorCroatia
5.5
BUDAI
Csanád Gyula
Hungary
5.9
IONAȘ
Vadim
Moldova
2.9
ARMESTO MÉNDEZ Irene
Spain
7.2
JEMELJANOV
Aleksei
Estonia
3.5
ARCHABOONYASEK Thongchai Thailand
6.2
OGNYANOVMichail
Belgium
4.4
STEPANYAN
RobertNetherlands
6.8
AZIM
Ughur
Azerbaijan
5.5
HEGEDIĆ
Ivan
Croatia
3.4
ABDELRAHIM
Youssof
Qatar
5.2
RAZBADAUSKAS Tomas
Lithuania
4.9
ALSHAKHS
Mazen Zaid A
Saudi Arabia
6.4
PAROJČIĆ
Đorđe
Serbia4.1
NUMANOVIĆ
Muhamed Bosnia and Herzegovina 7.6
AUGUSTO DE PAULA Jônatas
Brazil5
CARPENTER
Ruben Mason
Spain
2
FRÉCHETTELouisFrance
6.1
KALINAUSKAS Paulius
Lithuania
4.5
KELLIJS
Lukass
Latvia5.7
TONNER
Benjamin Patrick Austria
4.8
BÁLEK
David
Czech
8.1
GIURI
Andrea
Italy
4.8
WONG
Ka Wa
Macao
4.6

11.9
12.2
12.9
11.4
16
14.8
15.5
12.9
13.3
12.5
12.1
15.1
10.7
14.4
11.7
13.4
11
12.2
14.3
12.5
12.7
11.2
13.5
9.9
12.5
15.5
11.4
13
11.8
12.6
9.3
12.6
12.8

18.4
18.3
18.3
18.3
18.3
18.2
18
18
18
18
18
18
17.9
17.9
17.9
17.8
17.8
17.7
17.7
17.7
17.6
17.6
17.6
17.5
17.5
17.5
17.5
17.5
17.5
17.4
17.4
17.4
17.4

BronzeBronzeBronzeBronzeBronzeBronzeBronzeBronzeBronzeBronzeBronzeBronzeBronzeBronzeBronzeBronzeBronzeBronzeBronzeBronzeBronzeBronzeBronzeBronzeBronzeBronzeBronzeBronzeBronzeBronzeBronzeBronzeBronze— Honorable Mentions —Last NameFirst NameCountry/Region Exp.
VIRŠILAS
JokūbasLithuania
8.1
GIL-GARCÍA
JavierMexico4.8
RAMADHAN
Ahmad Nafi
Indonesia
3.1
PALMGREN
Alvin
Sweden7.8
MILLINGTON
Vincent
Canada7.4
AMARFIIȘtefanMoldova
4.2
KHAIRO ALSENDI Rose Abdulqadir ISaudi Arabia
3.5
MURPHY
AlastairAustralia
5.6
PROVAZNÍK
Pavel
Czech
5.4
SALIMOV
Husanjon
Tajikistan
4.7
FIALA
Mikuláš
Czech
5.8
NAJA
Muh. Zaidan
Indonesia
6.3
DORADEA MELÉNDEZ Miguel Isaias El Salvador
4
MRUG
EduardSlovakia
4.9
HE
Susan
Australia
5.5
GERALDESJoão
Portugal
4
VIRTANEN
OskariFinland
5.2
VAN HERBRUGGEN Cas
Belgium
5.5
ALAM
KM Meshkat Bin Bangladesh
2.7
LUVSAN
DulguunMongolia
6.7
SABIT
Ahmed Saad
Bangladesh
4.9
RISTOLAINEN
Eero
Finland
6.5
MUSUMECI
MatteoItaly
3.1
MILANOV
VladimirBulgaria
4
ZIGO
Matej
Slovakia
7.9
MAYYA
Anas
Syria
3.4
GRAUR
DariusMoldova
3.1

Theory Total
9.2
17.3
12.5
17.3
14.1
17.2
9.4
17.2
9.7
17.1
12.9
17.1
13.6
17.1
11.4
17
11.6
17
12.3
17
11.1
16.9
10.6
16.9
12.9
16.9
11.9
16.8
11.2
16.7
12.5
16.5
11.2
16.4
10.8
16.3
13.6
16.3
9.6
16.3
11.3
16.2
9.6
16.1
13
16.1
11.8
15.8
7.9
15.8
12.4
15.8
12.4
15.5

Medal
HM
HM
HM
HM
HM
HM
HM
HM
HM
HM
HM
HM
HM
HM
HM
HM
HM
HM
HM
HM
HM
HM
HM
HM
HM
HM
HM

73

DE HAAS
StanNetherlands
6.4
ISMAYILOV
Murad
Azerbaijan
2.9
OSTOJIĆ
MiodragBosnia and Herzegovina 3.1
RASMUSSEN
Benjamin Olander Denmark
6.8
PINTO
Ivan
Portugal
5.3
GUIMARÃES MELLO Matheus
Luxembourg
6.4
GELEV
Matej
Macedonia
4.2
GAGNIDZE
Bidzina
Georgia
3.4
PONTECORVO Bruno
Switzerland
5.1
WITSCHEL
Ludvig Steen
Denmark
4.4
ZADOROŽNAJA Olita Anastasija Latvia
5.5
EMIRZAS
Sotirios
Greece5.7KOMOČAR
LorenaCroatia
4.4
AIROUD
Mahmoud
Syria
1.3
KUBRICKÝ
Tomáš
Slovakia
4.5
EMILIJA
Nikolovska
Macedonia
4.8
ALTAMASH
Huzaifa
Pakistan
3.8
JACOB
BenjaminPhilippines
3.1
KRISTMANNSSON Jakob Lars
Iceland
5.3
OZOLIŅŠ
Toms
Latvia6.3
LEI
Chi Kun
Macao
6.4
SHAH
Aayan
Nepal
5.9
TURDUKEEV
Atai
Kyrgyzstan
4.7
ASMATULLAH
Muhammad Bilal Pakistan
2.2
VALAMAT-ZADE Matin
Tajikistan
4.1
VASQUEZ GARCIA Juan Esteban Colombia
5.2
GHULOMZODA Huseini
Tajikistan
2

9
12.4
12.1
8.4
9.9
8.5
10.7
11.4
9.3
9.8
8.7
8.4
9.7
12.8
9.5
9.1
10.1
10.8
8.5
7.5
7.4
7.9
9
11.5
9.4
8.2
11.4

15.4
15.3
15.2
15.2
15.2
14.9
14.9
14.8
14.4
14.2
14.2
14.1
14.1
14.1
14
13.9
13.9
13.9
13.8
13.8
13.8
13.8
13.7
13.7
13.5
13.4
13.4

HM
HM
HM
HM
HM
HM
HM
HM
HM
HM
HM
HM
HM
HM
HM
HM
HM
HM
HM
HM
HM
HM
HM
HM
HM
HM
HM

5.3.2 Special Prizes
Absolute Winner
YU, Bowen (China)
Best Performance in Experimental Examination
FAN, Collin (United States)
Best Performance in Theoretical Examination
YEVTUSHENKO, Feodor (United States)
ZHAO, Hanhong (China)74

5.3.3 Diversity commendation
A statement “Each country is encouraged to promote gender diversity within its team.” has been added to
the Regulations to the Statutes of IPhO. To promote this action, the IPhO2023 organizer has awarded“Diversity Commendation” to the following four teams which represented well balanced gender mixture andexhibited good team performance in the contest.
CyprusFranceIcelandUkraine75

5.3.4 Statistics of the contest results (score distribution)[Experimental exam (full mark = 10 X 2 = 20)]
Distributions of scores for Questions 1 and 2 of the experimental exam.
Experiment Q1Experiment Q2Distribution of the total score (Q1+Q2) of the experimental exam.

[Theoretical exam (full mark = 10 X 3 = 30)]
Distributions of scores for Questions 1, 2 and 3 of the theoretical exam.
Theory Q1

Theory Q2

76

Theory Q3Distribution of the total score (Q1+Q2+Q3) of the theoretical exam.

[Total Score (full mark = 50)]
Distribution of the total (experimental and theoretical exams) score and medal thresholds.

77

6. Organization and Logistics of IPhO2023
6.1 Organization of IPhO2023
6.1.1 Organization chart

Article of Incorporation of the IPhO2023 Association*
The objectives of the IPhO2023 Association are (1)to promote awareness of physics and physics
education and (2)to contribute to physics education reform in elementary/ secondary education stage
and to human resource development in physics area, through hosting of the International Physics
Olympiad 2023 in Japan (IPhO2023)
In order to accomplish the above objectives, the IPhO2023 Association undertakes following activities.
(1) Planning and implementation of IPhO2023(2) Communication and collaboration with the IPhO Secretariat as well as relevant domesticorganizations(3) Preparation for IPhO2023, including exam creation, venue setup, and public relations(4) Fund-raising for IPhO2023(5) Other necessary activities for smooth implementation of IPhO2023*English translation of the Articles of Incorporation (the original in Japanese)
The IPhO2023 Association was established in 2018 in accordance with the “Act on General
Incorporated Associations and General Incorporated Foundations” issued by the Japanese
government.
Address: Secretariat of the IPhO2023 Association
c/o Tokyo University of Science, 1-3 Kagurazaka, Shinjuku-ku, Tokyo 162-8601, Japan

78

6.1.2 IPhO2023 Local organizing committee

KOBAYASHI Makoto

AMANO Hiroshi

Chair, Organizing Committee
President,
IPhO2023 Association

Vice Chair,
Organizing Committee

KAJITA Takaaki

IYE Yasuhiro

Vice Chair,
Organizing Committee

Secretary-General,
Organizing Committee
Chair, Executive Committee
Board Member,
IPhO2023 Association

HAYANO Ryugo

SAKAKI Hiroyuki

Chair, Academic Committee
Member,Organizing Committee
Board Member,
IPhO2023 Association

Chair, Fundraising Committee
Member,Organizing Committee
Board Member,
IPhO2023 Association

RAWAT Rajdeep SinghSTANLEY Paul

President,
IPhO Secretariat

Secretary,
IPhO Secretariat

6.1.3 Organizing committee and board members
KOBAYASHI Makoto

AMANO Hiroshi

Chair, Organizing Committee
President,
IPhO2023 Association

Vice Chair,
Organizing Committee

KAJITA Takaaki

IYE Yasuhiro

Vice Chair,
Organizing Committee

Secretary-General,
Organizing Committee
Chair, Executive Committee
Board Member,
IPhO2023 Association

HAYANO Ryugo

SAKAKI Hiroyuki

Chair, Academic Committee
Member,Organizing Committee
Board Member,
IPhO2023 Association

Chair, Fundraising Committee
Member,Organizing Committee
Board Member,
IPhO2023 Association

DEGUCHI Yukichi

FUJII Teruo

Member,Organizing Committee

Member,Organizing Committee

FUJIWARA Makoto

FURUKAWA Kazu

Member,Organizing Committee

Member,Organizing Committee

79

GONOKAMI Makoto

HASEGAWA Mariko

Member,Organizing Committee

Member,Organizing Committee

HAYASHI Kayoko

HIRAMOTO Toshiro

Member,Organizing Committee

Member,Organizing Committee

HOMMA Yoshikazu

ISHIKAWA Masatoshi

Member,Organizing Committee
Board Member,
IPhO2023 Association

Member,Organizing Committee

ITOH Kimitaka

IWAKIRI Shoichiro

Member,Organizing Committee

Member,Organizing Committee

KITAHARA Kazuo

KYOTO Michihisa

Member,Organizing Committee

Board Member,
IPhO2023 Association

MATSUMOTO Yoichiro

MIKI Chitoshi

Member,Organizing Committee

Member,Organizing Committee

MIYAJIMA Kazuo

NAKAMOTO Akira

Member,Organizing Committee

Member,Organizing Committee

NAKAMURA Michiharu

NITTA Hideo

Member,Organizing Committee

Member,Organizing Committee

NOJI Hiroyuki

SHINODA KenichiMember,Organizing Committee

Member,Organizing Committee

TAJIMA Setsuko

TERUMICHI Yoshiaki

Member,Organizing Committee

Member,Organizing Committee

80

TOHYAMA Takami

TOKUNAGA Eiji

Member,Organizing Committee
Board Member,
IPhO2023 Association

Member,Organizing Committee
Board Member,
IPhO2023 Association

YOKOYAMA Hiromi

YUKI Akio

Member,Organizing Committee
Board Member,
IPhO2023 Association

Member,Organizing Committee

ARIYAMA Masataka

TANIMOTO Shigeru

Auditor,IPhO2023 Association

Auditor and Former Director,
IPhO2023 Association

6.1.4 Academic Committee
HAYANO Ryugo
Chair, Academic Committee of
IPhO2023
Professor Emeritus, The Universityof Tokyo

ITOH Kimitaka
Vice Chair, Academic Committee of
IPhO2023
Head, Theoretical Exam Subcommittee
Advisor to the Chancellor, Chubu
University

ARAFUNE Jiro
Member, Theoretical Exam
Subcommittee
Professor Emeritus, The Universityof Tokyo

FUKUSHIMA Kenji
Member, Theoretical Exam
Subcommittee
Professor, Department of Physics,
Graduate School of Science, The
University of Tokyo

KATO Takeo
Member, Theoretical Exam
Subcommittee
Associate Professor, The Institutefor Solid State Physics,
The University of TokyoKISHINE Junichiro
Member, Theoretical Exam
Subcommittee
Professor, The Open University ofJapan

SUGAWARA Yuji
Member, Theoretical Exam
Subcommittee
Professor, College of Science andEngineering,
Department of Physical Sciences,
Ritsumeikan University
YASUDA Masami
Member, Theoretical Exam
Subcommittee
Group Leader, Time Standards
Group,
National Institute of Advanced
Industrial Science and Technology

TAKEUCHI Kazumasa
Member, Theoretical Exam
Subcommittee
Associate Professor, Department of
Physics,
Graduate School of Science,
The University of Tokyo
FUKATSU Susumu
Head, Experimental Exam
Subcommittee
Professor, College of Arts andSciences,
The University of Tokyo

81

FUJII KenichiMember, Experimental Exam
Subcommittee
Invited Researcher (former Prime
Senior Researcher),National Metrology Institute ofJapan,
National Institute of Advanced
Industrial Science and Technology
SAKEMI Yasuhiro
Member, Experimental Exam
Subcommittee
Professor, Director, Center for
Nuclear Study,
Graduate School of Science,
The University of TokyoMIO Norikatsu
Member, Experimental Exam
Subcommittee
Professor, Graduate School of Science,
The University of TokyoYOSHIZAWA Masayuki
Member, Experimental Exam
Subcommittee
Professor, Department of Physics,
Graduate School of Science,
Tohoku University

HOMMA Yoshikazu
Head, Invigilation Subcommittee
Director, Organization for Innovationand Social Collaboration,
Tokyo University of Science

TOKUNAGA Eiji
Member, Invigilation Subcommittee
Professor, Department of Physics,
Tokyo University of Science

TSUNEYUKI ShinjiHead, Marking Subcommittee
Professor, Department of Physics,
Graduate School of Science, The
University of Tokyo

SHOJI Ichiro
Member, Experimental Exam
Subcommittee
Professor, Faculty of Science andEngineering,
Chuo University

ONO Yoshimasa A.
Member, Academic Committee
Part-time lecturer, Department of
Physics, The University of Tokyo

6.1.5 Executive committee
IYE Yasuhiro
Chair, Executive Committee of
IPhO2023
Head, Ceremony Subcommittee
Chancellor, Chubu University
Professor Emeritus, The
University of Tokyo

TOHYAMA Takami
Member,Organizing Committee
Board Member,
IPhO2023 Association

YAMASHITA Minoru
Head, Event Planning
Subcommittee
Associate Professor, Institute for
Solid State Physics,
The University of Tokyo

YOKOYAMA Hiromi
Member,Organizing Committee
Board Member,
IPhO2023 Association82

6.1.6 Event planning subcommittee (Excursion/cultural event team)
YAMASHITA Minoru
Head,
Event Planning Subcommitee
Excursion/Cultural Event TeamHAN Ruisi

KATABE Ai

Student staff leader,
Excursion/Cultural Event Team

Student staff leader,
Excursion/Cultural Event Team

OGURA Chiyori

OOKA AkiStudent staff leader,
Excursion/Cultural Event Team

Student staff leader,
Excursion/Cultural Event Teamand Newsletter TeamKUSUNO Sakura

SHINODA Erika

Student staff leader,
Excursion/Cultural Event Team

Student staff leader,
Excursion/Cultural Event Teamand Newsletter TeamTSUKIJI Natsumi

YAMADA Rino

Student staff leader,
Excursion/Cultural Event Team

Student staff leader,
Excursion/Cultural Event TeamYATSU Rikuo

BLOCK Ashley Miyuki

Student staff leader,
Excursion/Cultural Event Team

Student staff,
Excursion/Cultural Event Team6.1.7 Public relations subcommittee (Newsletter team)
TOHYAMA Takami

ONO Yoshimasa A.

Head,
Public Relations Subcommittee
Newsletter Team

MemberNewsletter TeamANDO Karin

JOKA Natsumi

Student staff,
Newsletter Team

Student staff,
Newsletter TeamKIMPARA Michiru

SASAKI Yasutaka

Student staff,
Newsletter Team

Student staff,
Newsletter Team83

6.1.8 Official Photographers

SHIMIZU Takeshi

OONO Aiko

Photographer

Photographer846.2 Co-Organizers and Supporters
IPhO2023 was organized under the auspices of the Ministry of Education, Culture, Sports, Science andTechnology (MEXT) Japan.

Ministry of Education, Culture, Sports,
Science and Technology (MEXT)
IPhO2023 was supported by the following co-organizers and special supporters, together with many otherindividuals and organizations:6.2.1 Co-organizers

The Physical Society of Japan

Japan Society of Applied Physics

The Physics Education Societyof Japan

The Biophysical Society of Japan

Japan Science and Technology
Agency (JST)National Institution for
Youth Education (NIYE)

National Museum of Nature and Science

The University of Tokyo

Tokyo University of Foreign Studies

Japan Arts Council

Tokyo National Museum

Tokyo University of Science

Tokyo City University

International Christian University

Sophia University856.2.2 Special supporters
Special supporters are companies and foundations that offered generous support to IPhO2023.
Some of the special supporters preferred to be anonymous. Although their names or logos are not shown
here, they are included in the number of supporters.
Diamond Supporters

Benesse Holdings, Inc.

CASIO COMPUTER CO. LTD.

Daikin Industries, Ltd.

Fujikin Co., Ltd.

NICHIA CORPORATIONTokyo Electron Limited

Toray Industries, Inc.
Sapphire Supporters

BUFFALO INC.

Hamamatsu Photonics K.K.

HIROSE ELECTRIC CO., LTD.

HORIBA, Ltd.

Honda Motor Co., Ltd.

Masason Foundation

Murata Manufacturing Co.,Ltd.

NGK INSULATORS, LTD.

Nikon Corporation

86

Rigaku Corporation.

RIKEN KEIKI Co., Ltd.

SCREEN Semiconductor
Solutions Co., Ltd.

Shimadzu Corporation

TOPPAN INC.

Toyota Motor Corporation

Toyota Physical andChemical ResearchInstitute

ULVAC, Inc.

The University of Tokyo Edge
Capital Partners Co., Ltd.

AGC Inc.

Asahi Soft Drinks Co., Ltd.

Dai Nippon Printing Co., Ltd.

DKK-TOA CORPORATIONDMG MORI CO., LTD.

FANUC CORPORATION

Hitachi High-Tech
Corporation

Inamori Foundation

JASCO Corporation

JEOL Ltd.

Kodansha Ltd.

MinebeaMitsumi Inc.

Mitsubishi Electric
Corporation

MUFG Bank, Ltd.

Sankei Giken Kogyo Co., Ltd.

Ruby Supporters

87

Takagi Co., Ltd.

Toshiba Corporation

Western Digital Corporation

YASKAWA Electric
Corporation

6.2.3 Supporters and donors
Special Supporters*
Diamond Supporter Companies
Sapphire Supporter Companies
Ruby Supporter Companies
Supporters
Supporting Members (companies and groups)
Supporting Members (individuals)
Donors (companies and groups)
Donors (individuals)

8
18
22
13
18
63
112

*Because some of the special supporters preferred to be anonymous, these numbers do notnecessarily coincide with the numbers of company logos shown above.

88

6.3 Logistics of IPhO2023

The National Olympics Memorial Youth Center (NYC)

6.3.1 Venue of IPhO2023
The National Olympics Memorial Youth Center (NYC)

89

90

View of NYC

91

92

Athletic Building

Arts Building

93Building A - Accommodation –94

6.3.2 Social activities – Excursions
Half-day Tokyo Excursion: A-1, A-2, and A-3

A-1: Yokohama

Yokohama Chinatown

Cosmo World

Highlights
Yokohama is a famous harbor city with an international seaport that was opened in the Edo period. Yokohama
has been vigorously acquiring new cultures and information from foreign countries and introducing first-timeever things to Japan from foods to a wide range of cultures, which entitles Yokohama as the birthplace ofJapan’s modern culture. This Yokohama course offers a tour of the history, culture, tourist places, and local
activities of the Yokohama area.
What can you do?
Schedule: NYC (National Olympic Memorial Youth Center) →(bus)→ Yokohama (free time) →(bus)→NYC
You can visit a variety of popular sightseeing spots in Yokohama.
Here is the example below ↓● Yokohama Chinatown○ You can grab delicious Chinese foods!
● Cosmo World○ Compact but varied amusement park famous for the Ferris wheel!
● Yokohama Landmark Tower○ Sushi, Studio Ghibli, Weekly Shonen Jump…everything is there!
● Harbor View Park
○ You can enjoy the perfect ocean view!
● Yokohama Red Brick Warehouse○ You can enjoy shopping at a historical warehouse!
● Cup noodle Museum○ Let’s make your original cup noodle!

95A-2: Asakusa & Ueno

Senso-jiNational Museum of Nature and Science

Tokyo National Museum
Highlights
Asakusa is the central “shitamachi” (downtown) in Tokyo. Asakusa is a town known for traditional performing
arts such as Kabuki. There still retains the old downtown atmosphere in Nakamise, one of the most famousstreets in Japan. The second town you will visit is Ueno, famous for its many cultural facilities. Since Ueno Park
opened as the first national park in Japan in 1876, Ueno has developed into a cultural city with many museums.
In this course, you will explore the Japanese history!
What can you do?
Schedule: NYC → Asakusa (free time including lunch) → Ueno (one museum) → NYC*For the Ueno area, you will choose either the National Museum of Nature and Science or the Tokyo National
Museum to visit. Below are some spots in this course.
● Nakamise (old shopping street famous since the Edo period (1603-1867), 89 shops, 250-m long)○ You will have Japanese foods and souvenirs (fees for buying souvenirs are not included) while
walking along Nakamise.
● Beautiful and famous scenery in the Asakusa area
○ You can take pictures of some famous spots: Tokyo Skytree and Kaminari-mon.
● National Museum of Nature and Science○ You can learn about the history of the Earth and Japan with various exhibitions. (e.g. fossils of
dinosaurs).
● Tokyo National Museum○ You can see various works of art from Asia, with a focus on Japanese art.

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A-3: Odaiba

JOYPOLIS

National Museum of Emerging
Science and Innovation

Highlights
Odaiba is a large landfill island in Tokyo Bay, famous for being the most modern active seaside place. There
are vast parks, large commerce facilities, sightseeing spots, etc. Its history goes back to the Edo period (16031867). When Commodore Perry visited Japan’s shores in 1853, the Edo government decided to strengthen
coastal defenses and started to build Odaiba. Until today, Odaiba has developed as a commercial and leisurearea. In this excursion course, you will enjoy the modern city and the cutting edge of science!
What can you do?
Schedule: NYC → Odaiba (JOYPOLIS / Miraikan) → NYC*In this course, you will choose either JOYPOLIS (A-3a) or the National Museum of Emerging Science andInnovation (“Miraikan”, A-3b) to visit.
Below are the main spots in this course.
● JOYPOLIS (an indoor amusement park using the latest technology)○ You can enjoy thrilling rides and activities.
○ You will experience exciting lights, sounds, and physical motions.
● National Museum of Emerging Science and Innovation (“Miraikan”)○ You will experience today’s technological progress, including space exploration and life science.

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Full-day Kanto Excursion: B-1, B-2, B-3, and B-4

B-1: Hakone

Hakone shrine

Black egg

Pirate ship ride

Highlights
Hakone is a mountainous area that has long been known as an important transportation hub since the
Kamakura period (1185-1333). Hakone has been famous for hot springs since the Edo period (1603-1868), andstill, many tourists visit Hakone for the sake of healing. One of the specialties in Hakone is the black egg. Sulfur
from the hot springs turns the egg’s color black. In this course, you can fully enjoy the nature of Hakone. We
hope you can see Mt. Fuji from the ropeway!
What can you do?
Schedule: NYC → Owakudani → Hakone En → Pirate ship ride → Hakone shrine →NYC
● Hakone Shrine○ Famous shrine with the historical Torii gate.
● Owakudani○ You can eat famous black-boiled eggs.
○ You may need to pay attention to the smell of sulfur wafting from the hot springs!
● Near the Ashinoko Lake
You can ride
○ Pirate ship
○ Ropeway98B-2: Tsukuba

KEK

KEK
Ropeway to
Mt. Tsukuba

Highlights
Tsukuba is widely known as a “Science City” of Japan located in the suburban area to the North of Tokyo.
Various institutions such as Japan Aerospace Exploration Agency (JAXA) and the Geospatial Information
Authority of Japan (GSI) as well as the University of Tsukuba develop the latest academic research with people
gathered from all over the world. In this Tsukuba course, you have an opportunity to experience the fundamental
technologies from High Energy Accelerator Research Organization (KEK), which will be followed by relaxing in
nature on the top of Mt. Tsukuba. You can get to the top by using a ropeway and cable car. From the peak, thevast view of the Kanto area can be seen.
What can you do?
Schedule: NYC → KEK → Mount Tsukuba → NYC★ Two-hour lab. tour of High Energy Accelerator Research Organization (KEK)○ Operate the largest particle physics laboratory in Japan★ Lunch at KEK★ Hike in Mount Tsukuba○ Ride on a cable car and ropeway.
○ Panorama view of Tsukuba and Tokyo○ Shrine at the bottom of the mountain99B-3: Nikko

Theater in the Edo Wonderland

Kegon Fall

Yomeimon in the Nikko Toshogu
Highlights
Nikko’s history as a religious place can go back to 766. Since then, not only majestic buildings but also beautiful
paintings or sculptures in temples and shrines have fascinated people for a long time. Also, Nikko has been
known to be an ideal place for leisure. Between Meiji (1868-1912) and the early Showa era, many foreignembassies built their villas in Nikko. If you join this course, you can relax in nature and visit famous shrines
constructed in Nikko. You can experience “live” Edo culture, too.
What can you do?
Schedule: NYC → Kegon falls → Nikko Toshogu → Nikko Edo-mura (Edo Wonderland) →NYC
● Nikko Toshogu (World Heritage)○ You can see traditional majestic architecture.
● Kegon fall
○ You can feel nature and relax.
● Edo Wonderland○ You can enjoy “live” Edo culture.

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B-4: Kamakura

Hachimangu Shrine

Kotokuin Temple

Hokokuji Temple

Highlights
Kamakura is a coastal town in Kanagawa Prefecture, less than an hour away from the south of Tokyo by train.
The town became the political center of Japan when Minamoto Yoritomo chose it as the seat for his new military
government in the late 12th century. Today, Kamakura is a small city but a very popular tourist destination.
Sometimes called the Kyoto of Eastern Japan, Kamakura offers numerous temples, shrines, and other historicalmonuments. In addition, beautiful Kamakura's sand beaches attract large crowds during the summer.
What can you do?
☆In this course, we don’t prepare a fixed route. You can choose where to visit according to your preferences.
●●●●

Hachimangu Shrine (National Important Cultural Property)○ You can enjoy the atmosphere of a historic shrine.
Kotokuin Temple○ You can see the Great Buddha, which is a symbol of Kamakura.
Hokokuji Temple○ You can enjoy a bamboo forest and matcha tea.
Yuigahama beach○ You can get in the sea and may take photogenic pictures.

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6.3.3 Social activities -- Japanese cultural experience
July 11 - 13, 4:00 pm – 7:00 pm

 Aikidō (Japanese Martial Art) experience (July 11th and 13th) @ 5th Gymnasium
Aikidō（合気道）is a sport trying to control your opponents by utilizing their attacks. Through practical exercises,
you will learn how to defend yourself in case of an attack. Maximum of 20 participants for a 30-minutes
session. Come to Reception Hall for registration.
 Sadō (Japanese Tea Ceremony) experience (July 11th and 13th) @ Oka Tei
In Sadō（茶道）experience, you will experience a tea ceremony and its preparation along with authentic
Japanese sweets and powdered green tea. Maximum of 15 participants for a 30-minute session. Come to
Reception Hall for registration.
 Shodō (Japanese style calligraphy) experience (July 11th and 13th) @ Lounge area near theInternational Conference Hall
Shodō（書道） is one of the traditional arts in which one expresses oneself with letters using a brush andsumi ink. In this experience event, you will have the opportunity to use a brush correctly to write letters on
Japanese paper.
 En’nichi festival: July 12th @ Reception Hall
En’nichi（縁日）is a traditional Japanese summer festival. In addition to playing old-style games (target
shooting, etc.) and enjoying small snacks, you will experience Bon Odori dancing around a “yagura” tower.
 Making your own “watoji” notebooks (July 11th-13th) and “uchiwa” fans (July 12th).
Make your notebook using traditional Japanese paper. Making an uchiwa (Japanese fan) with a picture ofyour design will also be a good memory of IPhO2023 Tokyo.
 Japanese traditional games (July 11th and 13th)
You will enjoy traditional games such as kendama, koma-rolling, origami making, etc.

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6.3.4 Social Activities --- Science and technology experience corner
July 11 - 13, 4:00 pm – 7:00 pm
at International Conference Room, International Exchange Bldg. 1F
The Science and Technology Experience Corner offers opportunities for hands-on experience with cuttingedge technologies and/or amusing games based on scientific principles. The exhibition corners are furnishedby volunteering companies who also contributed to IPhO2023 as special supporters.
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CASIO COMPUTER CO., LTD.
Brighten your summer with curiosity!
Fujikin Incorporated
Integrated Gas System Competition
Masason Foundation
Experience the world created by young talents of various nationalities and specialties
NGK Insulators, Ltd.
NGK SCIENCE SITE
Nikon Corporation
See physical phenomena for yourself!
Rigaku Corporation
Material analysis experience using portable and desktop analyzers
SHIMADZU CORPORATION
Analyze the caffeine content of commercial beverages!
Tokyo Electron Limited
Semiconductor Manufacturing Technology Experience Corner
ULVAC, Inc.
Hands-on vacuum experiment show103

6.4 IPhO2023 Handbook

CONTENTS
About International Physics Olympiad (IPhO)
IPhO 2023 Program
Excursions and Social Activities
The National Olympics Memorial Youth Center (NYC)
Important Notes
Participants (Team Profile)Students, Leaders, and Observers
Organizing Committee
Supperting Staff
Special Supporters

page
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28
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117
118

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6.5 IPhO2023 Newsletters
Newsletters were published everyday during the IPhO2023 period. The title “Butsuri” meaning “Physics” inJapanese were written in different typeface of Kanji (Chinese characters), Hirakata (cursive form of Japanesesyllabary), and Katakana (square form of Japanese syllabary)

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7. Feedback from Participants
We have sent questionnaire to the contestants (students), leaders and observers after the IPhO2023. About
80 contestants and 80 adult participants responded.

7.1 Feedback from Contestants on the Implementation of Examination
7.1.1 On the experimental exam
Correlation between the subjective rating of the difficulty level of the experimental exam by individual
contestants and theiru actual score.

[Comments by contestants on the experimental problems]
 I found that setting up the experiments were particularly time consuming, not leaving so much time to actuallycomplete the experiment. The experiments themselves were interesting.
 Experiment 2 was very delicate and sensitive to initial imprecisions in the setup. I did not manage to getaround to E1.
 Although problems required time to assemble, I really enjoyed all of experimental test
 It was really long to set up and it wasn’t really easy so we would have time to do both experiments really good Conceptually and theoretically the problems were of a normal IPhO difficulty. However, the setup for theexperiments was difficult and time-consuming which didn't help to score as much as we have studied for the
olympiad.
 I found the experimental problems very interesting. Even though the process of assembling the kit was moretime-consuming than I had thought, I really enjoyed them.
 There was not enough space. Second table would be preferred for optics. Hole instead of crease in the optics
aparature would be also great.
 easy technically, but big time pressure The second experiment required little thinking. One had to do very precise measurements which were hardto achieve with the given tools. I really did not like it.
 Too much setup The main difficulty I came across was managing my time during the exam. The experimental kit was incredible
and very fun to setup. But it also took a very long time before being able to make our first measurements so
I couldn't get to explore the questions as far as I would have hoped...
 It's very cool to assemble the kit
 It was awesome to assemble everything ourselves, and it demanded a lot of mastery and precision. The only
problem is working on optics, light and diffraction without being able to be in the dark, that made things a lot
more complicated than they should have been. I noted that we were very guided on what protocol to follow,
maybe it would be a good thing to also test the candidates on their ability to create a smart protocol because
it is also a crucial part of experimental physics.

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It was great being able to set up everything on my own, however I lacked time
Way too much text so i missed important things. I heard there was a misunderstanding with the number ofcharacters in the statutes
Second one was extremely difficult.
The time was too limited!
Took too long to set up and it was hard because we had to be very precise
A lot of strict steps, but no creativity
fun experiment problems overall, question 2 is kinda hard to assemble
It takes a lot of time to set up E2
setups were so nice but the optic rails where not effective and setting up was difficult in second experiment.
although i wish i had more time to do the experiments, for my own pleasure:)Long rather than difficult
fun experiment problems overall, question 2 is kinda hard to assemble
It takes a lot of time to set up E2
setups were so nice but the optic rails were not effective and setting up was difficult in second experiment.
although i wish i had more time to do the experiments, for my own pleasure:)Long rather than difficult
FUN BUT CHALLENGING TO SETUP.
E2 too delicate, better if sturdier.
Preperation took way too long, the questions were quite easy, but the time required to get to the questions
was too long
The experimental problems both took quite a long time to set up, which meant that you had to be doing anexperiment for quite a while before being able to get points.
There was a lot things to do. Also experimental sets were too complex
The first experiment was very simple to understand and gather data, however, the second experiment wasvery time-consuming, and sometimes hard to understand.
Assembly of E-2 (optical problem) was especially finicky and time-consuming.
A bit lenghty(the instructions were very clear, but it took a lot of time to assemble the experiment and makethe measurements)
The problems were really interesting, but the setup and the calibration of the equipment took too long.
Quite simple phenomena represented in some really ingenious experiments. The experiments were reallywell explained.
the experimental apparatuses were far too complicated and took too long to set up. the problems were notconceptually difficult, but they were nearly impossible to finish because of the aforementioned issue.
Should have turned off the lights in the exam hall for Q2
The questions themselves were not that difficult but it was difficult to do everything because of lack of time.
Very interesting problems! But they were a little bit too difficult for me - I felt that I didn't understandanything...
I thought they were very fun! Though it seemed that many people complained that it took a long time to getstarted.
The experimental problems were really interesting, because of its difficulty level
The experiments itself weren't that hard, but it took quite a long time to build them. In my opinion, a bit too
long.
Experimental problems were really interesting. I liked both of the questions
Setup took too long, instructions unclear for how many data points to take for problem 2
I still don't understand why there was values like 11.3, 11.4 mm,.. while minimum division is 1 mm. Problems
were so good, it didn't take all of the time to assemble the setup. They were a bit difficult
Very exciting and terrible
Very solid problems. Loved the oscillations one, although I didn't have time to do the interesting parts of thebirefringence one.
I liked the problem with the oscillator very much, it was a nice and easy electronic setup but still the theory behind it was hard.

1097.1.2 On the theoretical exam
Correlation between the subjective rating of the difficulty level of the thoretical exam by individual
contestants and their actual score.

[Comments by Students on the theoretical problems]
 I found that the theoretical problems were easier than most ipho problems, but the problems themselves
were quite interesting applications of theory.
 I thought that very interesting topics were chosen, especially connecting the Brownian motion to Nikon’s
stand at the scientific events.
 It was fine
 Very interesting problems!!
 The theoretical problems were very clear and challenging. I loved them.
 The tasks weren't hard but tedious. It wasn't about thinking, but about repetitive use of math.
 very hand-holdy, do this, calculate this, but the calculations weren't easiest
 Mostly fine.
 T3 felt easier than the rest
 It was fine.
 Very mathematical They were gorgeous, all in very different ways. It was just the right amount of mathematics, and I believe it
is a complicated thing to balance. We were able to see 3 very different things in very satisfying ways, to geta full grasp at them, thank you so much. I have small issues with them, first question of Q3 about thebounce of a water droplet, we are given k such that Cinetic energy is equal to k times the potential energy
loss, (0,06) and with k the problem is trivial. The only real physical difficulty is to find k, so it is hard to see
the point of the question. In the last question of Q1, part E, there is an indication to use Newton's second
law, when really we should be using energy, and it is what the official correction does, it was a mistaking
indication. Otherwise, everything was amazing. Maybe I wish there were a few less guided questions,where we could be more autonomous. I am aware that it is complicated because it leads to tedious andsubjective moderation with team leaders afterwards, and most of the questions should be guided, butmaybe I would be nice to have one or two more opened questions (like Fermi's questions), which are really
relevant for testing physicists.
 Quite mathematical, as most of it didn't really need a brilliant physical idea and then you could solve in an
elegant way. I'd like to have more of this There should be less questions focusing only on mathematical tasks and more focusing on creative thinking
and physics intuition.
 Good concept, but not hard math

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was not as hard as i thought, but still relatively challenging
standard. completely ok.
The stated problems have been already seen as similar tasks previously, a lot of math was applied insteadof neat physics problems. The physics knowledge actually was not test, instead, long mathematical tasks
without much of the physical insight.
i liked the theoretical problems
The marking schemes were too focused on the mathematical part, and did not focus on the physics, butrather punished mathematical mistakes.
I think that the first two problems were too much about math than actual physics, and some people, like me,
might be frightened just by looking at the problem.
Too heavy on math, especially the Brownian motion problems.
Seemed a bit too short and too easy. The last problem(water tensions) was especially short
The questions were relatively easy, but exemplified interesting phenomena and principles.
While the problems were quite easy to solve, I really enjoyed the concepts presented in the problems.
the problems were too short and easy to effectively identify the level of the contestants
Very good - there were both problems I could solve and problems I couldn't.
Theoretical problems were quite easy
Theoretical problems were fun to solve. I liked mostly theoretical problems
nice to have some more variety in problems set like electricity (felt quite mechanics oriented)
Interesting problems
I found no drawbacks in theoretical problems
I want cry again huhu
Problems were pretty thought-provoking. They don't seem to be that diverse though (mostly mechanics).
I liked the problems, especially the first part of the neutron star problem about stability, although it was aquite easy part the calculations are cool to do (I always like formulas that look hard but are not and have aphysical meaning).

7.1.3 On the exam environment and operation70

How do you evaluate the examination environment and operation?
(booth set up, calculator, support to help flags, etc.)

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【Comments by Students on the Examination Environment and Operation】
 Very comfortable air and temperature compared to outside, nice tables with enough space Examination environment and operation were greatly arranged. Places in which we solved problems havebeen perfectly done. Examination operation was well organized. For me it was the best examination
environment.
 Hard to coordinate 2 experiments on the table provided.

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Everything worked perfectly.
Very square
I loved jelly like drink
It would have been nice to have people who know what we're doing there to help because when othercompetitors’ equipment just wasn't working the people helping thought it was supposed to be the way andthis seriously impacted his performance.
apart from the excessively many steps necessary to assembly the experiments, everything went well
Everyone in my room are so niceeeee
very nice calculators! i'm glad we got them home, together with the clocks
The environment and operation were excellent. The effort and organization was noticed.
the functionality of the calculator was very limited
Add numbers to the rulers
On the first day the examination hall was too hot.
"The snacks during the exams were amazing :)maybe make it clearer before the competition that we won't be able to bring any food during the exam (Itook a lot of snacks with me to Japan that I couldn't use) and that all connected device have to be handed
out for a period 4 days."
I had difficulties to understand the announcement
Everything was so well organized, it was amazing. A shame that the announcer in green room on theexperimental test day spoke terrible English, it was impossible to comprehend.
The tables were too low, or at least the frames underneath the table surface were too low for me. I wascompletely unable to have my legs underneath the table, my knees hit the metal frame. As a result I could
only sit leaning forward a lot which was quite uncomfortable.
The setup was very well prepared and everything was explained very clear
The table wasn't high enough for my legs to fit under.
Everything was perfectly setup. Wonderful!
chair height was about 5 cm shorter than my legs lengtha bit of confusion with the rooms (I was at first sent to the wrong room), but everything else was great
Everything was really timely and well prepared.
It was very good, hard to cheat for anyone but still you had enough space and snacks so you could do thetests in a comfortable way.
It was very good except for the air conditioning. The room would get hot and it was difficult to concentrate atsome points.

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7.2 Feedback from the Leaders and Observers on the Implementation of Examination
7.2.1 On the experimental exam【Comments by Leaders and Observers on the experimental problems】
 Too long description, too much text
 I am happy with the experimental problems. I was glad to see that they requite some assembly and setup
skills, which is not always the case. On the negative side, I was surprised that the same markers checkedboth experiment and theory. It is never done like this.
 Very good and challenging problems
 interesting, well done The setup part took a substantial part of the time allocated - though admittedly the instructions were clear.
Yet this way of distributing the time for the experiment, handicapped the students who were not too muchfamiliar with the working of the instruments provided.
 The experimental problems were very interesting and beautiful.
 The tasks were interesting, however, the text of the tasks was too long. We should follow the rules and notexceed 12000 characters.
 Great questions and ingenious apparatus. Would have preferred a shorter question statement.
 Excellent problems
 The problems were interesting with the theory behind them not overly difficult, and they focused on
experimental skills (which is good), even though the setup of the equipment took quite some time. The
marking was also on point.
 very good E2 is well designed, and the use of wooden parts for optomechanical mounts splendidly reflects Japanese
craftmanship. E1 is also robust. I like how E1 requires a little bit of assembly as well.
 The optical set up was well built and had a Muji vibe to it!
 A bit too long for student to finish all in 5 hours.
 The problems are exciting when it asks students to perform operations to set up the experiment. However,the number of tasks needs much more time than 5 hours.
 It took to much time for students to assemble both experimental kits. One of the experimental tasks shouldhave been assembled and ready to be used.
 Excellent problems, but a bit too long for 5 hours. Perhaps having the experiments partly set up would havehelped students.
 Maybe it was good to give some marks to the student who could build the setup of the experiment even hedid not make any measurements, because building the setup itself was not easy especially in E2.
 long
 There was too much text for the students to process. I would've preferred shorter problems and lessinstructions on what the students needed to do to conduct the experiment.
 Experimental questions were very good.

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Too much composition of delicate parts prior to measurements
The experiments were interesting but they required a lot of time to carry out. To mount and tune the setup of
the second experiment was not a easy job.
Problems were very well designed. What makes these problems different from typical IPhO problems is thatthe assembling and tuning of the apparatus had an important part to play, and if not done carefully, a lot ofpoints would be lost on the tasks due to the results being not accurate enough. This is definitely a useful
lesson for the contestants as in real physics experiments, design and assembly of the apparatus are crucial.
Overall, there was a lot of work to do (assembly and executing all the tasks). Due to this, our students
managed only to start the second experiment. While it would have made sense to reduce the volume oftechnically easier tasks so that more students would have been able to reach the more demanding tasks,
longer problems have their own merits (e.g. using the apparatus to a fuller degree).
Q2: It was desirable to clearly indicate that wavelength increments should be measured at 5 nm or lesswhere necessary.
The moderating processes were stuck by unreasonable principles. In our case, three international referees
had already agreed with the correctness of our students' answers, but still had to force the moderator of
Taiwan team to make a small reasonable change. The marking scheme is too simplified and discourages
the students' learning.
The procedures for the experimental problems might be too long.
I also consider the problems themselves and their preparation excellent.
Very good practicals. Maybe too many detailed instructions making it difficult to complete in the time
available. Would be better if the final section of each question could involve some creativity or insight rather
than just the process of taking and analysing results, however, this is difficult to achieve. The apparatus wasvery good.
A student who build the experiment correctly without measurements (running out of time) get zero, thesame mark as a student who don't touch the experiment !
They were very well designed. The Kibble balance actual.
Especially two experiments with many settings gave problems in time.
To do all the experiments was very time-consuming.
Both needed a lot of time before doing the actual experiment (for points). One such an experiment should
be fine. Not two. The (average) score on the second experiment supports this.
The experiments are well designed. It is great to require students to carefully assemble the equipment.
For the experimental problems maybe some less structuring of the problems could be better. Less direct
instructions how to measure something.
Experimental Problems were too long.
"Nice and well-prepared experiments, thank you! I also liked the idea that students should have assembled
their setup themselves and some points were given for validation that the setup worked correctly.
Some issues:
During the exam one our student had to spend additional time dealing with not-working power supply (it had
to be replaced twice!). It is good that organizers had spare ones available (good practice for futureorganizers), but more thorough inspection is needed prior exams.
(Noticed only during the marking) How to measure oscillation amplitude in Exp 1 D2 part with precision of
0.1 mm?"Problem 2 required a careful setup. Since the problems description were too long it took too much time totranslate.
I haven't solved the experiments step by step myself, but the quality of the kits seemed very nice.
Fine experiments, the first one is important for students - new definitions in SI
Great problems, but a little too much to do for the students.

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7.2.2 On the theoretical exam【Comments by Learders and Observers on the theoretical problems】
 Also too much text, they should be well shorter Interesting exam. Also, good to see reference to Japanese nature. On the negative side, I was surprisedthat the same markers checked both experiment and theory. It is never done like this.
 Good problems
 The theoretical problems were interesting and addressed a series of practical applications, the tasks were
well structured and clearly formulated.
 The tasks were appropriate, however, the text of the tasks was too long. We should follow the rules and notexceed 12000 characters.
 Great ideas in the questions, but too many subparts telling the students what to do The problems were quite interesting and accessible to the students in my opinion. A good variety of different
areas of physics was implemented throughout the three problems. The marking was also very good and allissues with the marking were satisfactorily resolved during the moderations.
 very good Well balanced and span full contents of syllabus.
 I thought the contexts were well thought of, making links to the host country.
 It is good and interesting problems, but need more challenging.
 Excellent problems and a good level of difficulty Good subjects
 suitable
 I think the problems were of appropriate difficulty, but there was too much text and instructions. This madeeach individual problem just a little bit easier and shifted the focus of the exam on reading comprehension
and efficient text processing.
 Very nice questions, I appreciate that two of them dealt with problems of modern physics.
 Too many characters used for introducing the problems
 All three problems dealt with fascinating physical phenomena which bring students to the forefront ofmodern physics. For instance, the dynamics of water droplets on superhydrophobic materials is a topic
actively studied by modern fluid dynamics. That's why I enjoyed the problems very much. The problems
were reasonably challenging; to get full marks, one had to have a solid understanding of the topics at hand,
and to be able to execute mathematical calculations fast and without mistakes. What I missed myself a little
was that there were no tasks which were conceptually very difficult. But regardless of that, the eventual
distribution of the theory scores was very nice. This means that the overall difficulty of the problem set wasvery appropriate.
 Too much hint in the problems

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The problems are appropriate, but the marking scheme is unreasonably rigid.
Very nicely put problems, in my opinion, albeit rather mathematical.
The problems were fairly standard. If you could work through the maths, you could get through the problems
in the time available. They were appropriate for the syllabus. However, it would be better to try and include a
section at the end requiring insight and a deep understanding of the physics, rather than just maths. This isdifficult to achieve.
A lot of math. Not a lot of 'conceptual' questions.
"The order of questions could be reconsidered, unless you intentionally arranged so.
In Q1, Part E seems to be somewhat ad hoc addition and might have given a little confusion."
Due to serious shortening of the problems just one day before the disscussion the problems might be muchworse, but somehow they appeared nice at the end. The problem 2 should probably not be shortened.
Marking scheme for all the problems should be more detailed and some better evaluation and notion of the
propagating errors should take place. Students displayed correct reasoning but using some wrong numbers
they got at previous tasks no points were given even if they displayed the full comprehantion of the physics
in particular task. This is remark also for experimental problems (about more detailed marking scheme andpropagating errors). It was good that we got the marking scheme immediatelly, but maybe the possibility toadapt the marking scheme after the competition, when you see which common mistakes were done by thestudents and which alternative ways of reasoning they took, should be appropriate.
Theoretical Problems were very good.
Markers were too strict regarding foolish arithmetical mistakes made by students (like 1/3+1=7/3) thatchange only numerical value of the final answer, regardless of the correct solution method.
Since the problems description were too long it took too much time to translate.
Very nice problems, some sentences have been a bit wordy, but I think that was already realized that it
might be good for future years to have some native english person that reads the exams in advance. Also
the marking was very similar to our own, and the moderations seemed to be fair.

7.2.3 On the International Board Meeting: environment and operation

How do you evaluate the environment andoperation of the International Board Meetings?
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15
10
5
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excellent very good

good

fair

poor

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【Comment by Leaders and Observers on the environment and operation of the International Board Meetings】
 It would have been greater if all delegation members (leaders, observers) could have been together
 Everything work very well, excellent support. Except for the absence of tea!
 I feel like the org was oftentimes not agressive enough. I personally missed some of the critical votings that while sitting in the room. More should be done to focus the crowd, because everyone is busy. The org
did not approach teams to understand their comments. Often refused remarks were marked as "withdrawn"- while the leaders did not actually withdraw them.

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Nice event
I appreciated the very good organization and punctuality for each board meeting, as well as the constructive
discussions within the board.
It was very good that there were always drinks and snacks during the translation time.
Procedure seemed somewhat inefficient. For example, question writers would often scroll through changes
in a long PDF document, without sharing the PDF file itself, making it hard to see globally what waschanged. Sometimes question writers would read through every comment when it would have been more
efficient to group similar ones together, or quickly skim over very minor ones.
The overall atmosphere was pleasant and the organization was on point. It was my first time as a leader in
the Olympiad and I thoroughly enjoyed the Board Meetings.
very good
Our seats were right on the exit, and people kept walking through our seating
It was a good move to use Zoom for Obsevers to tune in.
Both lectures were really interesting and inspiring young talented students. I would like to thank both
Japanese Nobel laureates as well as IPhO 2023 organizers.
At times, discussions felt unneeded and that the question writer should just make the decision rather thanput small edits to a vote. But the operation of the meetings improved a lot from the experiment to the theory.
no proplem
Some of the problem discussions could've been better organised. I feel like we didn't make use of the fullpotential of the OlyExams tool when it came to voting. There should be a clear procedure on how we deal
with the problem discussion because oftentimes we as leaders didn't quite know what was going on andwere afraid that the issues were raised would get lost. Perhaps the IPhO Secretariat should chair the board
meetings? Also it would be quite useful if there was more time to read the problems and give feedback plus
another 30 mins or so after feedback is submitted to vote on feedback; this would make it easier for the hostto decide which issues are important.
very well prepared and controlled (esp Paul) discussions on change of IPhO regulations
Thank you very much for your hard work well done!
The meetings were well conducted. Thank you. For the future we have yet to find a perfect solution to
manage the discussions on the tasks.
Facilities were good, printing efficient, WiFi was good. The meetings were well run. However,communication was sometimes lacking, especially regarding timings and schedules. Communication wasvery succinct but needs to be repeated more often!
nice
It would have been better if the leaders and observers had been together (but I understand it is not easy tofind a large enough meeting room).
There is room for improvement. I believe that feedback on the exam questions should be semi-anonymous.
Displaying the name of the country does not add any substance (physics) to the comments. On thecontrary, it may allow implicit biases to creep into the evaluation. It may also encourage an unhealthy
competition to provide more edits. However, the authorship of edits should be accessible to the organizers
to prevent any abuse of the system.
Good spirit, but updated/final versions came with an annoying delay.
Voting (also during translation) remains strange. Some leaders are present but do not vote.
good
It was better if leaders and observers were in the same room.
Some technical difficulties while voting, and sometimes it seemd helpfull that Paul guided that discussion alittle bit. Maybe with a different person leading the discussion (from the japan organisation team) somediscussions would have been a bit faster or less confusing. But from what I retain it was more smooth
towards the end of the week (I was most of the time in the observers room, not strictly following all
discussions).
Sometimes difficult to follow the meeting from the observer room, but apart from that everything went well.
And the meeting was very good and efficiently lead!

1177.3 On the Cultural and Social Events
7.3.1 Special lectures by Nobel laureates【Comments by Students on the Special Lectures by Prof. Kajita and Prof. Amano】
 The lectures were amazing, It wasn't the conventional boring physics presentation, Prof. Kajita and Prof.
Amano, really did a great job, also I think that anybody not related to physics could understand thempresentation.
 We really liked whole presentation and we are very honoured to listen to nobel lauterates
 Really great Their lectures were awesome. It was honor that we heard lectures by two Nobel Laureates in Physics. I
sincerely thank Professor Takaaki Kajita and Professor Hiroshi Amano for things that they taught us
 very interesting and enjoyable Very interesting, really enjoyed them The lectures were interesting and helped me make decisions for my future.
 Prof. Kajita's lecture was very exhaustive on the topic of neutrions. We learned a lot from his talk and hiscomments and questions. Prof. Amano's lecture sent some very valuable messages about finding passion
in your work and never giving up.
 I enjoyed both of them and I liked that their styles were so different. While the first lecture exposed a short
glimpse into neutrino research, the second lecture was more relaxed and inspiring for achieving high goals
in life.
 I thought that the lectures added perspective to the Olympiad, especially its competitive aspect.
 Quite awesome and cool
 Inspirational Interesting and well-organized Very enlightening Hmmmm, He is wonderful, amazing, handsome
 Very good and inspiring! Hope to view it again online( hopefully it is available on the website later)!
 Interesting and informative
 It would be nice to have the slides or at least the recordings of the lectures.
 I learned a lot from the special lectures, which were very enjoyable and educational
 the neutrino lecture was boring and the blue LED lecture was funny (in a good way)
 I found the lectures very interesting, and it was an honour to listen to them!
 Nice, thank you again!!
 Interesting Interesting interesting materials and fun interesting materials and fun Very interesting Very interesting oth lectures were interesting and they complemented each other very well.
 They were great, I really enjoyed them Thank you for these very instructive lectures.
 The first one was really good Grateful for the lectures
 It was an honor to have them talk to us about there research and research life, truly inspiring. The issue wasthat they struggled a little with English, so it was hard to understand, and they read a lot what was written
on their PowerPoints, which you shouldn't do.
 I suspect most of the student were expecting more details about the research and more rigorous
explanations
 The first lecture was good and I was pleasantly surprised by the second one. I found it actually very usefulfor my future career.
 An awesome mix between science and life advice.
 Both were interesting. I would even spend more time here.
 Were extremely inspiring and fun! Amazing!
 I can't really emphasize enough, how stunning and valuable those lectures were.
 Inspiring lectures detailed. a bit fast at some points and a bit slow and some other points.
 Amaizing! Deep insights, personal angle, interesting topics!

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Loved them! It was really interesting to hear about their research/how they progressed from highschoolers/undergraduates just like us to being extraordinary.
They were both very nice! The neutrino one actually thought me things I didn't know before without
overusing my brain (After the tests I wanted to give my brain some rest), while the other was an interestinglife.
Really enjoyable, straight to the point lecture that left me with a thought.

【Comments by Leaders and Observers on the Special Lectures by Prof. Kajita and Prof. Amano】
 Excellent and the right balance of inspiration and level of physics detail. Were they recorded and can they
be put on Youtube for other students?
 Very interesting talks, in particular the one by Prof. Amano Totally loved; Super inspirational and important. The best I have seen on any of the IPhOs. These are true
heroes.
 Great experience did not attend
 Very nice.
 "The special lectures by Prof. Kajita and Prof. Amano represented a very special and unique moment in mylife.
 Thank you for this extraordinary opportunity to attend the captivating lectures of the two Nobel laureates
and to discuss with Prof. Kajita.
 Both very interesting each in its own style and content.
 Very good, and inspiring for our students!
 It was my honor to attend lectures from Nobel laureate.
 It was truly an honor attending the lectures and I believe both the students and the leaders/observers foundthem equally interesting. The lectures were also not overly technical in nature, which I very muchappreciated - the professors focused more on their life paths and stories as well as some advice for theaudience, which made for a very pleasant experience.
 very good Excellent speakers! Excellent lectures!
 Kajita sensei's neutrino lecture is useful and informative, while Amano sensei's is inspiring and more
personal. I think students may enjoy's neutrino topics more, but as an adult I like the story of the birth ofblue LED and the struggle of a scholar.
 Very interesting and different from previous Olympiads
 Very interesting and intriguing Excellent. Very inspiring and motivating lectures. Students need to hear that science means hard working.
 Excellent
 Very impressive and useful lectures.
 excellent
 A spectacular event!
 I really enjoyed the lectures! I also believe the lectures were very useful for the students for planning theircareer.
 Excellent
 They were very useful lectures for the students.
 The lectures are great and inspiring. The speakers in the small hall was broken, and the online video was
disconnected from time to time.
 Excellent
 Especially the lecture by Prof. Amano was heartwarming and inspiring as it was not a normal lecture but
rather a story of a professional life.
 The lectures were great but the quality of the video feed was surprisingly poor for such a venue which
distracted from the lecture for leaders in the small lecture theatre.
 Very nice
 they were nice to hear
 Nice combination.
 Very interesting and encouraging especially for students
 good

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Very well prepared lectures, paying attention to the audience, I am sure every student was able tounderstand and grasp the meanings. Extraordinary event that we were able to meet 3 Nobel prize
laureates, who were not disappearing immediately after the lectures:)Those lectures were very interesting for leaders, observers and specially for students.
I loved it!
Unfortunately I have been late and couldn't join.
Great!
Good

7.3.2 Science and technology exhibitions【Comments by Students on the Science and Technology Experience Events】
 They were interesting events. The things that they showed and taught us were so awesome that I want to go
there again
 Besides the CASIO booth, the events I found most interesting were building the Da Vinci bridge and the test
for caffeine in everyday drinks, but I can't remember the names of the entities that provided these experiences.
 The expositions were really interesting, and I loved the fact that all booths gave us free souvenirs, which madethe experience even more memorable
 Nikon was the highlight.
 Thank you for letting me play rush E at the casino piano booth Interesting, inspirational, cool gifts
 I love ittt engaging experience i dont like science during my free time
 Good fun
 I only had time to see the booths I checked above and all were very interesting!
 I didn't see most of them, so in the multiple choice questions I can't fairly answer.
 They were a bit like the companies were trying to recruit you, what wasn't very pleasant, but it was ok.
 It was not interesting at all.
 Camera booth with milk crowns was really cool, but can't remember the company
 Insightful, really loved NGK sweets and the bridge building booth excellent. one of my best moments in this journey.

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Good for general schools, but not technical enaught for a physics olympiad
It is a very nice way to let the sponsors promote themselves without giving boring speeches.

7.3.3. Cultural experience events【Comments by Students on the Cultural Experience Events】
 Each of them was so enjoyable. It was one of the best experiences in my life. I really want to try them again
 Great, perhaps more planning to ensure everyone can have an equal chance to do certain activities assome people were at shodo for a long time and some of our team only were given time for 1 before they
were asked to leave Really enjoyed trying to learn to play with Koma. There is a certain beauty to knowing you suck at a gamethat is a pastime for primary schoolchildren. The staff was really nice and really helpful!
 The events were fun and a great way to bring back souvenirs from Japan.
 Everything was perfect.
 It was so beautifully organized and it was a great opportunity to experience various aspects of the Japaneseculture. All of them were so exciting, I LOVED IT.
 Based YMCA
 Well orgonised
 I did not have time to attend all the events, but I appreciated all of them the new act, amazing experience good and fun
 very cool
 I found the cultural experience events interesting, and it was exciting to be able to experience a taste ofJapanese culture.
 Really fun
 fun
 I think there should be some instructions in Japanese traditional game I loved that we were able to get a taste of traditional Japanese culture Thank you all for organizing these events!
 I really enjoyed the Shodo Experience. All cultural events were very interesting Some of my best memories from the trip are from the summer festival. In general the Cultural Events wereso much fun, we were so lucky to have them organized for us.
 I unfortunately didn't participate in the tea ceremony but I'm sure it would have been enjoyable.

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I was really nice events, weEverything was awesome!
Amazing
I loved ennichi the most. Everything else was perfect too!!
i missed much of them. tea party was excellent.
We had the posibility to experience stuff, that most turists don't get to experience. A lot of different stuff, andthe free will to pick and choose made it one of the hightlights
I liked them very much, it is important that not only science but also culture is respected in concern withdecisions in life (like (not) building a star observatory on top of a holy mountain), so culture should definitely
be represented on an event like IPhO as well.
I really enjoyed them all. It gave a great opportunity to experience Japanese culture as well as creating
lovely memories with my friends.

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7.3.4 Stage performances1227.4 On the Overall Operation and Hospitality

How do you evaluate the overall operation of
IPhO2023? (All Participants)
14%

2%
1%

excellentvery good
good

27%

56%

fair
poor

【Comments by Students on hospitality of IPhO2023 (accommodation, food, student supporters, etc.】
 It was a bit of problem for us halal students because we were often put in the same place as vegetarians
because we can eat every meat except pork
 I loved the hospitality of all staff of IPhO2023, the food was very different to our main country both in termsof flavour and quantity, but it gave a sense of the Japanese culture, which was pretty cool.
 food was disgusting (especially the tasteless rice), hospitality couldn’t be better, everything else was fine The accommodation was nice. I liked place where I lived. It was comfortable. Foods were so delicious. Eachof student supporters were great, nice and kind, especially our student supporters. Every excursion that wewent was so fun and exciting. I thank all IPhO 2023 organizers and people that helped in this olympiad fromthe bottom of my heart student supporters were fantastic and very friendly. More variety of fruit and veg for meals.
 The hospitality in general was great. The food could have been more suited to non asian contestants.
Student supporters were excellent, but they had difficulty communicating in english.
 "The food was good, and I was never hungry during the IPhO.
 Our student supporter was very nice, and I don't think our experience would have been as fun without her.
By helping us deal with all the details of navigating Tokyo and it's metro, Seiko made our stay in japan
flawless. Besides being a very interesting person herself, having someone who could explain to you thecustoms of a foreign culture was invaluable (things that most people take for granted in japan, like leaving
chopsticks in rice being disrespectful). I am really grateful for all her help!" Food was very strange sometimes (especially for Europeans), but nevertheless a unique experience.
Accommodation in single-occupancy rooms was good offering privacy, but the queue for the shared
showers was long. Amazing toilets by the way downstairs in international exchange building.
 Accommodation was bad, food at fuji cafeteria was terrible. Our student supporter was really sweet andhelpful.
 The Wi-Fi provided was quite poor, the showers were stuck at 40ºC water and our student supporter barely
spoke English. The food was good.
 We loved our student supporter, she was really nice and pleasant to talk to.
 The food was really good for cafeteria food, the accommodation was also good but my experience in Japanwas so good also due to our student supporter, who was great! She brought us to so many great
restaurants and her general vibe was so nice. She made the experience incredible
 Ja!
 "Accommodation was fine but without wifi connection
 Halal food didn't have great variety
 Student supporter is 11/10"
 My name is registered wrongly :(

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It should have been hosted in a hotel
The food could have been better — for the first few days there weren't seperate vegetarian options so thevegetarian competitors had only rice. The accommodation was good and our student supporter wasamazing :)I would have preferred for the accommodation to be at a more comfortable location (i.e. a hotel), but I
enjoyed that we had air conditioning in our rooms. The volunteers were also great!
Sending my gratefulness to Ami
Excellent! The buffet-style food served is awesome and tasty. The student supporters are friendly and help alot.
The food was delicious. The supporter did a really good job and was fun.
one of the things i loved the most at the olympiad! and lots of love for our amazing supporter!
Excellent organization, generous, and willing to help in everything they could. The timetable and the guides
were selected in such a way that we could enjoy the olympiad, have cultural experiences, and have time tovisit Japan. My only complaint is two things. On one hand, the early dinner schedule you couldn't control
anyways), and the poor design of the backpacks (even a child knows that the logo must be big, bold, and in
the middle of the backpack, it is common sense). The
it would be cool to have more quality meals outside of the canteen
The student leaders were very hospitable and helpful, and I appreciate having them there to lead us aroundand teach us a bit about Japan!
The accommodation and the food we were served there was bad. Old, tiny rooms, dirty bathrooms andterrible food. Ik the budget is always tight but please, if you can, change the accommodation the next time
Good
Good
showed great hospitality, NYC was a good site to held IPhO. The rooms, however, weren't that great, but it's
still manageable
showed great hospitality, NYC was a good site to held IPhO. The rooms, however, weren't that great, but it's
still manageable
The accommodation and food were subpar, but the student supporters i met were really nice people.
Food was rather poor quality"Accommodation: very good, private room + lots of social areas
Food: good but not enough food during ""light lunch""
Student supporters: our guide (Chihiro) was truly amazing and all supporters that I met were friendly andhelpful"Our student supporter was great, he was always really nice and helped us with everything we needed.
I wanted to thank all organizers and people involved in the competition. It was a truly unforgettable
experience for me! Every step of the organization was very neat and precise which let me enjoy this weekeven more. Again a great thank you to you all!
Maybe the portions of food were too small but it was overall a great experience!!
The guides were exceptional, taking care for us
Our student supporter spoke our language (French) and it changed everything for us, it was amazing.
A bit more varied food was welcome
The cafeteria definitely could have been better
Both the accommodation and the food In cafeteria Fuji weren't great. The food was kinda bland and theaccommodation was small and the facilities (showers etc.) lackluster. The showers only being available from17:00-23:30 were quite a nuisance for example.
It would be better if accommodation was in some hotel instead, with better service. Combining vegetarian
food with halal food was too bad, the only thing we ate is rice, we aren't used to eat vegan food.
Extremely bad accommodation and foodEverything was good. Our guide was amazing.
"Our toilet wasn't working :(Otherwise"
It was all amazing, extremely well organized!
Accommodation was bad, and meals were good
Very poor accommodation and food, but good enough, I suppose. Student supporter was incredibly helpful!
Food was good! But having to make our bed was very new to me"i will miss you so much. sorry for being late most of the time:_)i learn many thing from you society. i think its so rare to have a chance to have a trip to japan, especially forme. so thanks a lot from anyone who have a hand in this event. ありがとうございます."

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Accommodation good, it had ac, but some of the restrooms were closed. Food was sub par, the food we
had on the excursions was leagues better. Our student supporter(s) were really enjoyable people that we
got to know.
Our student supporter was amazing! The housing/food seemed pretty standard.
Anything was really good, except for the food in the Fuji cafetaria, which I didn't like so much; on excursions
and after the closing ceremony we went eating in restaurants and it was the best food I've ever eaten!
Going to a Japanese restaurant (or for that matter, any restaurant) in Belgium will always be adisappointment since it will be very hard for them to beat the Udong we ate with our guide, Amika, in a verysmall restaurant where only locals came.
"I really liked the aspect of having all the events concentrated at the same place, the NYC. By that way, itcreated more opportunities for us to communicate and make friends with students from other countries. We
had a better experience than staying in hotel, and I hope that the next IPhOs will be held the same way.
We really loved our first student supporter. She had a nice personality that we enjoyed every second being
with her. Going on excursions with her made the experience much more enjoyable and memorable in myopinion. It was very sad that they had to change our student supporter due to the student working hour law.
And it was hard to getting along with our new student supporter as she stayed silent most of the time."
Everything perfect, at least 9.5/10 rate

【Comments by Leaders and Observers on the Overall Operation of IPhO2023】
 I participated as a leader in many editions of IPhO, but IPhO2023 impressed me in a very special way,
through absolutely everything. IPhO2023 has been a complete success!
 "For the most part the organisation was very good.
 The fact that during the opening and closing ceremonies, there was no adequate room for all attending
participants was something new for me, although the first IPhO I participated in dates back to 1998.
 I would complain also on the airport pickups. You guys made us wait to take several teams at once. We
didn't do this to you...
 Check in system at hotel. Waiting for a long time.
 Also, I believe that students awarded honourable mentions should also be invited on the stage of theclosing ceremony and receive a congratulations round af applause, as is customary.
 Other than that, local organisers, along with the members of the IPhO secretariat performed in a way mostuseful for the best outcome of this years contest."
 Only problem: ensure there is sufficient seating for leaders and students to sit together. The audio and video
quality in the small hall were very poor.
 Everything went smoothly and was well-coordinated.
 hotel check in should be earlier at leader arrival Most of the events are well prepared. A little disappointed during the opening ceremony where leaders wereseparated from the students due to the hall capacity
 Generally well-run and I enjoyed the whole stay there. Thank you so much!
 A very well organised IPhO - thank you.
 good Almost everything was fine. The only thing I did not understand was the participation of the Russian teamusing the name "Oly team of individuals", under the leadership of four observers. In my opinion the Russianteam should not have been allowed to participate.
 late opening of rooms on arrival day, inconvenient for exhausted travelers
 This was definitely one of the best IPhO-s.
 Except for the residence of the leaders on the last day at the National Olympic Youth Centre. So
unorganized and poor planning Thank you for organising IPhO 2023. it was a wonderful event.
 Everything ran on time in a professional manner The retransmission of the opening ceremony to the separate room for the leaders and observers did notfunction very well (butI understand it could be difficult to obtain a room big enough for 700 persons).
 The organisation was okay and we appreciate the effort in helping us with sleeping places before and after
the olympiad!
 Opening and closing: housing small. Not fun to look at a screen. A livestream for parents at home could benice!
 We did not like the coordination of transportation to the airport at the end of the Olympics, as the buses
were limited and not available at suitable times for the delegations’ trips.

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Sincerely appreciate the effort by the organizer, especially on their prompt and appropriate responses to
unforeseen issues. Well done.
I was happy to see that mixed gender teams were awarded for their good overall results!
It was better to stay in original hotel until last day, leaving hotel before closing ceremony and displacement
to art hall building with our luggage was very hard.
Punctuality in holding meetings and programs was excellent"Overall very smooth organisation!
Almost everything is acceptable except for the last day to spend one night at the National Olympic YouthCentre before departing back home. The schedule is so unorganized for the check in time . No one knows
what is going on. The schedule was announced to be 2 pm and kept postponing over and over again.... untillate in the evening around 18:00. This should be organized better than this. I should say it is quite
unorganized . This was my first experience in Japan in last 20 years that never happened before. Usually,
the Japanese way to organize is precise with a flawless plan.
One point that was a bit unlucky is that the observers had to be seperated from the leaders during the
problem discussion/translation. In the Swiss team we have been in total 5 leaders, so it was no problem toarrange that we could work in teams of 2 and 3, often we even mixed with the austrian team. But it was a bit
said to see that some other observers had to work isolated from their team.
From our Leader-1 I got the feedback that she really appreciated that she could follow all the discussions
live in the main room. This showed to me that this is indeed of importance, and it would have been nice if itwould have been possible for observers and leaders to be in the main room. But of course I understand thatthe space is limited... Same applies to the opening ceremony, where the sound and image have been rather
bad quality... But the closing ceremony was really nice (there I could join in the main hall)
Typical Japanese, this match our perception of Japan126

8 IPhO2023 in Photos
8.1 Opening Ceremony
Secretary General IYE explaining the flow of ceremony.

Masters of ceremony.

Opening Address by the Organizing Committee Chair KOBAYASHI Makoto

Minister of MEXT NAGAOKA Keiko

IPhO President RAWAT Rajdeep

127

128

8.2 Setting up the exam venue
The exam booths were set up in two gyms in the Athletic Building of NYC.

Exam compartments were designed by FUKUSHIMA’s group at Tokyo City University.
Partitions were made of cardboard, and could be assembled and dismantled without special tools.
They can be re-used as partitions of emergency evacuation sites in an event of natural disasters etc.

129Compartment

Desk

Stationaries

Sign flags.
Experimental kits130

8.3 International board meeting
International Board Meetings were held in NSH where leaders and observers of participating countries/regions
were accommodated.

Presentation of the exam problems

Inspection of the experimental kits.

131

IT technical team in preparation of IT environment for the International Board Meetings.

Pigeon boxes for printout delivery.

Coffee and midnight snacks.

Display of the status of translation submission

1328.4 Examination

133

Monitoring camera

134Checking of the answer sheets etc.

135

Contestants relieved from pressure of exams.

136

8.5 Excursions (half day, metropolitan area)1378.6 Cultural events

138

139

140

8.7 Science and technology experience corner1418.8 Excursions (full day, Kanto area)

142

143

144

8.9 Special lectures by Nobel laureates
KAJITA Takaaki

AMANO Hiroshi

1458.10 Final International Board Meeting146

8.11 Closing Ceremony

KOBAYASHI Makoto, Organizing Committee Chairgiving an opening address.

HAYANO Ryugo, Academic Committee Chair
explaining the exam problems and marking results.

IYE Yasuhiro, Executive Committee Chair introducing the team of student support leaders

147

YOKOYAMA Hiromi presenting special “Diversity Commendation” to the teams with gender diversity.

Medal presentation
Bronze medals presented by RAWAT Radjeep, STANLEY Paul and SAKAKI Hiroyuki

Silver medals presented by AMANO Hiroshi and KAJITA Takaaki.

148

Gold medals presented by KOBAYASHI Makoto.

Special awards, Best Performance in Experimental and Theoretical Exams, and The Absolute Winner.

149

Best performances in experimental and theoretical exams.

Invitation to IPhO2024 by the Iranian leader SHIRZAD

The Absolute winner.

Closing Address by the IPhO President RAWAT

150

8.12 Farewell Lunch

151

152

Afterword
As the title of Chap. 2 “Long and Winding Road to IPhO2023” conveys, it was a long and laborious
enterprise to host an International Physics Olympiad. Since the official kick-off of the Organizing Committee
on May, 2016, the core members tackled seemingly endless list of tasks. The hardest part of the tasks wasthat we had to make up a plan without clear prospect for the financial basis. As stated in Sec. 2.4.1, wewere supposed to fundraise about 150 million JPY to meet the estimated total cost. The economic situationin Japan was not favorable and the outbreak of COVID-19 caused further damage. Fortunately, we wereable to secure support from numerous companies and individuals who understand the importance of IPhO
event, so that we could host IPhO2023 with not so luxurious but decent accommodations and hospitalities.
We are pleased to receive mostly positive evaluations by the participants from all over the world.
Although the overall operation of IPhO2023 went relatively smoothly, there were a few incidents thatmight have derailed the plan. Firstly, COVID infection cases took place both in the NYC and the NSH during
the final few days. The moderation sessions were conducted with those who proved negative in the antigen
test. Luckily, the infection did not spread, so that we were able to complete the IPhO2023 programs andsee off the delegations to their return trip. Had the infection cases occurred in the earlier part of IPhO2023,
the whole schedule would have been severely scrambled.
Secondly, as we uploaded movies and photos on the IPhO2023 website, access increased. Our server
was forced to shut down on account of DDoS attack. Had it occurred during the most crucial periods ofteam registration and/or in early July when last minute correspondences were made with team leaders, theoperation might have been paralyzed.
In any event, we are happy to be able to complete the mission of hosting IPhO2023 with a lot of help
from people involved with the contest and entertainment and with financial support from the Co-Organizers
and Supporters. We thank the participants from around the world for joining IPhO2023 and make it
successful. Echoing the title of Chap.2 “Long and winding road to IPhO2023”, our personal recollection of
IPhO2023 is “All is well that ends.”

153

Appendix 1
Exam Questions
andModel Answers

Experimental
Examination

Experiment

G0-1
English (Official)

General Instructions
Failure to comply with any of the following conditions may result in disqualification.
The exam is worth a total of 20 points and lasts five hours.
When to start and finish up the examination and when 15 minutes remain before the end of the examination will be indicated by your Invigilator.
Do not open the envelopes nor boxes until instructed to do so.
The following items are provided for your use on the table: (1) a ballpoint pen, (2) a mechanical pencil,(3) a plastic eraser, (4) a scale ruler, (5) a scientific calculator, and (6) a digital table clock.
During the exam:• Use the ballpoint pen provided. If you use the mechanical pencil to draft your notes, figures, tables
and graphs, never fail to trace the outlines of the final version with the ballpoint pen.
• Use the dedicated sheets labeled A for your final answers. Fill in appropriate sections with youranswers and necessary observations. Draw graphs as required. Cross out any unneeded answers.
• Blank working sheets labeled W are provided for drafting. Use the designated ones. Cross out any
unneeded answers and rough work that do not need to be graded. Use only the front face of each
sheet and keep the margin outside the border clean.
• Additional working sheets labeled Z are available upon request. Raise the "Help" flag and let theInvigilator know.
• Keep your answers concise and legible. Use equations, logical operators, symbols, and sketches
that best convey your thoughts. Avoid being lengthy and wordy as the markers may not be multilingual.
• Uncertainty quantification is not required unless otherwise specified. On the other hand, you may
decide how many data points or measurement runs are needed unless instructed otherwise.
• You will be video-recorded for fairness and security purposes. Do not leave your booth without
permission. If you need a washroom break or any other assistance, raise the flag(s) marked "Toilet","Water", or "Help".
At the end of the exam:• Stop writing immediately when the end of the exam is announced.
• Put all the sheets in the windowed envelope for each question. Organize them faceup in the following order: cover sheet on top, question sheets (Q), answer sheets (A), working sheets (W), andadditional working sheets (Z), if any. Arrange them according to their page numbers. In the final
check, make sure that your ID, name, and seat number on the cover sheet are visible through thewindow. Leave only the General Instructions (yellow sheets stapled) on the table.
• You Invigilator will let you know when you can leave. Do not take anything with you. Time permitting, put everything back as it was. Your cooperation would be greatly appreciated.

Q1-1

Experiment

English (Official)

Mass Measurement (10 points)
In this experimental problem, a measurement of mass is attempted. We further measure the massutilizing the resonance characteristics of the harmonic oscillator.
Experimental setup
Below is the list of parts (Fig. 1). The number of the parts is given in [ ] if only there are two or more.

Figure 1: The experimental apparatus set.
1. Mounting base:Note: magnet unit on the base creates the height-independent uniform radial magnetic fields warranted near the center of the magnet pair to within ±3 mm in height.
2. (Oscillator) support
3. Thumbscrews [2]:Note: Remove 2 and 3 from 1 in the as-received package for use.
4. Shim (washer) [6]Q1-2

Experiment

English (Official)

5. Cylindrical oscillator
6. Rubber bands [6]7. Markers [2]8. Weights [5]9. Tweezers
10. Mirror
11. Riser block
12. Power supply (PS):DC or AC mode is toggled on.
In the DC mode, it works as the constant-current source. Turn the knob labeled “DC Vol” to adjust
the current. The magnitude of current is obtained from the voltage between “DCmon” and “DC
GND” using the conversion factor 1.00 A/V.
In the AC mode, it functions as the voltage source with a fixed amplitude. Turn the “AC Vol“ to adjust
the voltage. The AC current is obtained from the AC voltage between “ACmon” and “AC GND” using
the conversion factor 0.106 A/V. The frequency (Freq.) is tunable by using the “Coarse” and “Fine”
tuning knobs.
13. Battery holders [2]
14. Batteries [8]15. U-shaped crimp terminal wires [2]16. Alligator clip wires [2]
17. Digital multimeter (DMM):
Turn the knob to select an appropriate measurement mode, "DCV", "ACV", and "Hz". Note that thedisplayed value of the AC voltage indicates the root mean square (RMS) value, i.e., the effective
value.
Modeling the system
Figure 2 is a simplified model of the experimental setup. It is essentially a driven mass-on-spring oscillator.

Figure 2: Harmonic oscillator model.

Q1-3

Experiment

English (Official)

The relevant parameters are:• 𝑀 : mass of the (cylindrical) oscillator• 𝑚: mass per weight• 𝑁 : the number of weights• 𝑔: acceleration due to gravity• 𝑘: effective spring constant pertaining to the vertical motion• 𝑧: oscillator height (or displacement)• 𝑧e : oscillator height at which a force balance without gravitational and electromagnetic forces isestablished.
• 𝐵(𝐵′ ): magnetic field applied to the main (control) coil
• 𝐿(𝐿′ ): length of the conducting wire of the main (control) coil
• 𝐼(𝐼 ′ ): current flowing through the main (control) coil
• 𝛼: positive coefficient of drag force
The equation of motion is given by(𝑀 + 𝑁 𝑚)d2 𝑧d𝑧= −(𝑀 + 𝑁 𝑚)𝑔 − 𝑘(𝑧 − 𝑧e ) + 𝐵𝐿𝐼 + 𝐵′ 𝐿′ 𝐼 ′ − 𝛼 .
d𝑡2
d𝑡

(1)

Installation of the oscillator
1. Remove the support from the mounting base. Wrap four rubber bands around it in a grid pattern(See Fig. 3(a)).
2. Insert the cylindrical oscillator from the scale side into the square opening amid the crossed rubberbands. Place the wire leads on the other side of the scale. (Fig. 3(b)).
3. The oscillator is designed to hang on the support with four rubber bands and eight little hooks (redcircled in Fig. 3(c)). When properly implemented, one rubber band loop forms a truncated rhombus
with two hooks above and below the support level in the side view.
Note: In this experiment, we can assume that the effective force due to the rubber bands obeys
Hooke's law.
4. Refix the support to the post diagonally with two thumbscrews. The scale has to stand upright on
top, not on the side of the binding posts (Fig. 3(d)).
5. Stand the oscillator upright. Its axis must be aligned vertically and shared with the magnet unit.
6. The main coil should sit near the middle of the two magnets when at rest, which can be confirmed by
the distance between the upper surface of the lower magnet and the lower surface of the oscillator
being 3 to 5 mm (Fig. 3(e) red arrow). If it is low, put the shims between the binding posts and the
support (Fig. 3(f) red arrows). If it is high, turn the post of the magnet to remove it and add theshim under the post (Fig. 3(f) yellow arrow).
7. Expose the sticky surface of the double-sided adhesive tape on the marker (Fig. 4(a)). Glue themarker to the tiny little floating shelf on the oscillator to measure the height (Fig. 4(b)).
8. Set the mirror on the riser block (Fig. 4(c)). Secure a clear vision of the marker from above throughthe mirror (Fig. 4(d) red circle).

Q1-4

Experiment

English (Official)

Figure 3: Installation of the oscillator.

Figure 4: Installation of the marker and mirror.

Wiring1. Locate and pull gently the correct pair of wires leading to the main (M) and control (C) coils (Fig.
3(c)) from inside the oscillator (Fig.3(b)). Check to see if the enamel has been stripped off from theloose ends.
2. Loosen the screw on the binding posts M+ and M- to allow for gaps. Use the lower gaps for thewiring (Fig. 5(a), (b)). The polarity check will follow soon.
3. Wire the binding posts labeled C+ and C- likewise. (Either polarity is acceptable.)Experiment

Q1-5
English (Official)

4. Place the batteries in the battery holders and secure connections with PS (CN1, CN2) (Fig. 5(c)).
5. Connect the binding posts M+ and M- to the DC output (DC+ and DC-) on PS using the U-shaped
crimp terminal wires.
6. Toggle on DC and power up PS.
7. Turn the “DC Vol.” knob to adjust the current. Check to see if the oscillator moves upward by 2 mmor higher. If downward, swap the wires for polarity reversal and try again.
Caution: Hot parts. Beware of coils and magnets. Put the DC output down to the minimum at theend of each step.

Figure 5: (a), (b) Binding posts wired, (c) The whole setup wired including PS and batteries.

Oscillator test
1. Connect the M+ and M- binding posts to the AC output (AC+ and AC-) with the crimp terminal wires.
2. Toggle on the AC and power up PS.
3. Turn the knob labeled “AC Vol.” clockwise starting from the minimum up to a quarter turn. Tune
the frequency with the “Coarse” control knob to start oscillation.
4. Adjust the AC output voltage and frequency to make the oscillation about 𝐴 = 3 mm in amplitude(Fig.6). If the oscillation is unstable, adjust the oscillator settings as appropriate.
5. Disconnect M+ and M- and connect the C+ and C- binding posts to the AC output.

Q1-6

Experiment

English (Official)

6. Power up PS to start oscillation again.

Figure 6: Oscillation behavior as seen through the mirror.

Part A. Hooke's law and electromagnetic forces (2.4 points)
A.1

Draw in the answer sheet the magnetic field lines created by the two identical
disc-shaped magnets with their N poles facing each other.

0.4pt

A.2

Connect the M+ and M- posts to the DC output. Couple the DMM with the terminals for DC current readouts using the alligator clip wires (Fig. 7).
Read the oscillator height 𝑧 at null DC current without a weight, i.e., 𝑁 = 0.
Record it in Table A.2.
Place a weight (𝑁 = 1) on a circular shelf hanging out from the inner wall of thecylinder and record the height 𝑧 at which the oscillator comes to rest.
What is the DC current 𝐼 flowing through the main coil to bring the oscillator
back to where it was without a weight?
Repeat the measurements with increasing 𝑁 up to 5 to fill in Table A.2.

0.6pt

Q1-7

Experiment

English (Official)

Figure 7: The test leads of the DMM connected. The oscillator with a weight on the right.
A.3

Draw a graph showing the relationship between the number of the weights 𝑁Δ𝑧and the height 𝑧. Obtain the slope 𝑎 = Δ𝑁
and its uncertainty from the graph.

0.7pt

A.4

Draw a graph showing the relationship between the number of weights 𝑁 andthe current 𝐼. Obtain the value of 𝑏 defined as 𝑏 = 𝑁𝐼 and its uncertainty fromthe graph.

0.7pt

Part B. Induced electromotive force (3.0 points)
B.1

Suppose that an AC current at frequency 𝑓 is applied to the control coil withouta weight. Given that the oscillator height varies sinusoidally with time𝑧 − 𝑧0 = 𝐴 sin(2𝜋𝑓𝑡)

0.2pt

(2)

where 𝑧0 is the height for the force balance and 𝐴 is the amplitude of the oscillation, write down the expression for the amplitude 𝑉 of the induced electromotive force in the main coil.
B.2

Connect the C+ and C- posts to the AC output. Connect the DMM to the “Fmon”
and “AC GND” to read the frequency.
Adjust both the AC frequency and the output voltage to produce a steady oscillation of appropriate amplitude. Measure the frequency 𝑓B and record it in theanswer sheet.
Couple the DMM with the binding posts M+ and M-. With the frequency fixed,vary the output voltage
and measure the oscillation amplitude 𝐴 and the AC√voltage 𝑉 ′ (𝑉 ′ = 𝑉 / 2) induced in the main coil. Fill in Table B.2 as appropriate.

0.5pt

Q1-8

Experiment

English (Official)

B.3

Draw a graph showing the relationship between the amplitude 𝐴 and voltage′
𝑉 ′ . Obtain the value of 𝑐 defined as 𝑐 = 𝑉𝐴 and its uncertainty from the graph.

0.7pt

B.4

Calculate 𝐵𝐿 and its uncertainty using the results of B.3.

0.4pt

B.5

Using the results of A.3, A.4, and B.4, calculate the values of 𝑚 and 𝑘 and quantify their uncertainties. Use the acceleration due to gravity, 𝑔 = 9.80 m/s2 whereappropriate.

1.2pt

Part C. Mass-dependent resonant frequency (2.3 points)
For the following experiments use the main coil to drive the oscillator. Change connections accordingly.
C.1

Write down the expression for the resonant frequency 𝑓 of the oscillator with
𝑁 weights. Use the spring constant 𝑘′ during motion, which is different than 𝑘.

0.2pt

C.2

Drive the oscillator by coupling AC power to the main coil. Measure the resonant
frequency 𝑓, for different number of weights, 𝑁 = 0 to 5, and write down thevalues in Table C.2. Avoid jumping weights.

0.5pt

C.3

𝑚
Using the results of C.2, draw a graph to obtain 𝑀
𝑘′ and 𝑘′ . Write down theobtained values in the answer sheet. If you need to calculate any additional
physical quantities, write them down in the blanks of Table C.2.

1.0pt

C.4

What is the value of 𝑀𝑚?
Calculate 𝑀 and 𝑘′ using the results of B.5.

0.6pt

Part D. Resonance characteristics (2.3 points)
When a periodic force of amplitude 𝐹AC and frequency 𝑓 acts on the oscillator without a weight, theoscillation amplitude of 𝐴 is well described by the following with resonance characteristics:
𝐴(𝑓) =

1𝐹AC⋅.
28𝜋 𝑀 𝑓0 √(𝑓 − 𝑓0 )2 + (Δ𝑓)2(3)𝛼. This equation only holds in the frequency range where |𝑓 − 𝑓0 | ≪ 𝑓0 is relevant.
Here Δ𝑓 = 4𝜋𝑀

In this part, the resonance characteristics are used to obtain the mass of the oscillator, 𝑀 , assuming thatEq. (3) is always valid.

Experiment

Q1-9
English (Official)

D.1

Drive the oscillator by coupling AC power to the main coil. Adjust the frequency
and output voltage to produce a resonance with appropriate amplitude.
′
Record the AC voltage 𝑉AC
between the “ACmon” and "AC GND" in the answer
sheet.
Using the results of B.4 and the conversion factor 0.106 A/V, calculate the amplitude 𝐹AC of the periodic electromagnetic force acting on the oscillator.

0.4pt

D.2

Record in Table D.2 the amplitude 𝐴 of the oscillation as the frequency 𝑓 is varied. A constant amplitude 𝐹AC of the applied force must be maintained throughout the measurement.
Draw a graph showing the relationship between the frequency 𝑓 and the amplitude 𝐴.

0.9pt

D.3

Using the results of D.1 and D.2, obtain 𝑀 .

1.0pt

Experiment

A1-1
EnglishMass Measurement (10 points)
Write down the numbers 0 to 9 in the following table:
0

1

2

3

4

5

6

7

8

9

0 1 2 3 4 5 6 7 8 9Part A: Hooke's law and electromagnetic forces (2.4 points)
A.1 (0.4 pt)

S
N

N
S

A.2 (0.6 pt)
𝑁

𝑧 /mm

𝐼 /A

0

12.8

0

1

12.2

0.103

2

11.6

0.213

3

11.1

0.323

4

10.7

0.423

5

10.2

0.524

Experiment

A1-2
EnglishA.3 (0.7 pt)

13

z /mm

12

11

10
0

1

2

3

4

N
The slope and uncertainty are read from the lines plotted on the graph.
10.15 − 12.70
Δ𝑧== −0.51𝑎=Δ𝑁
510.20 − 12.60
𝑎+ == −0.48
5
10.10 − 12.80
𝑎− == −0.545−0.48 − (−0.54)
Δ𝑎 == 0.032

𝑎 = −0.51 ± 0.03 mm

5

Experiment

A1-3
EnglishA.4 (0.7 pt)

1
0.8

I /A

0.6
0.4
0.2
0
0

1

2

3

4

N

The slope and uncertainty are read from the lines plotted on the graph.
0.53
𝐼== 0.106𝑏=𝑁
50.55= 0.110
𝑏+ =
5
0.505
𝑏− =
= 0.10150.110 − 0.101
Δ𝑏 == 0.0052

𝑏 = 0.106 ± 0.005 A

5

Experiment

A1-4
EnglishPart B: Induced electromotive force (3.0 points)
B.1 (0.2 pt)

𝑉 = 2𝜋𝑓𝐴𝐵𝐿

B.2 (0.5 pt)

𝑓B = 15.85 Hz

𝐴 /mm

𝑉 ′ /V

0.5

0.024

1.0

0.048

1.5

0.071

2.0

0.099

2.5

0.124

3.0

0.146

Experiment

A1-5
EnglishB.3 (0.7 pt)

V' /V

0.2

0.1

0
0

1

2
A /mm

The slope and uncertainty are read from the lines plotted on the graph.
0.147
𝑉′
=
= 0.049
𝑐=
𝑁
5
0.150
𝑐+ =
= 0.050
50.144= 0.048𝑐− =50.050 − 0.048
Δ𝑐 == 0.0012

𝑐 = 0.049 ± 0.001 V/mm

3

Experiment

A1-6
EnglishB.4 (0.4 pt)
√ ′
√
√
𝑉
2𝑉
2𝑐
2 × 0.049= 0.000696 Vs/mm = 0.696 Vs/m
𝐵𝐿 =
=
=
=
2𝜋𝐴𝑓B
2𝜋𝐴𝑓B
2𝜋𝑓B
2𝜋 × 15.85
Δ(𝐵𝐿) = 𝐵𝐿 ⋅

Δ𝑐
0.001
= 0.696 ×= 0.014 Vs/m𝑐
0.049

𝐵𝐿 = 0.696 ± 0.014 Vs/m

B.5 (1.2 pt)
√
√
𝐼
𝑉
1
2𝑐
2 × 0.049
𝑚𝑔 𝐵𝐿
⋅
=
⋅
⋅ =𝑏
= 0.106 ×= 0.0075 kg = 7.5 g𝑚=
𝐵𝐿 𝑔
𝑁 2𝜋𝐴𝑓B 𝑔
2𝜋𝑔𝑓B
2𝜋 × 9.80 × 15.85
The principle of the Kibble balance (watt balance)
Mechanical power: 𝐹 𝑣 = 𝑁 𝑚𝑔 ⋅ 2𝜋𝐴𝑓B
Electrical power: 𝑉 𝐼

𝐹𝑣 = 𝑉 𝐼
Δ𝑚 = 𝑚 ⋅ √(

Δ𝑏 2
Δ𝑐 2
) +(
) = 0.4 g𝑏𝑐𝑚 = 7.5 ± 0.4 g
𝑘=−

7.5 × 9.80
𝑚𝑔=−
= 144 N/m𝑎−0.51

Δ𝑘 = 𝑘 ⋅ √(

Δ𝑚 2
Δ𝑎 2
) +(
) = 11 N/m𝑎𝑚

𝑘 = 144 ± 11 N/m

Experiment

A1-7
EnglishPart C: Mass dependence of resonant frequency (2.3 points)
C.1 (0.2 pt)

𝑓=

1
𝑘′
√
2𝜋 𝑀 + 𝑁 𝑚

C.2 (0.5 pt)
𝑁

𝑓 /Hz

1/𝑓 2 /s2

0

15.96

0.003926

1

13.03

0.0053902

11.33

0.007790

3

10.13

0.009745

49.06

0.0121858.45

0.01401

Experiment

A1-8
EnglishC.3 (1.0 pt)

2

1/f /s

2

0.02

0.01

0
0

1

2

3

4

5

N

𝑚
𝑀
The additional quantities 1/𝑓 2 are calculated in Table C.2. Then, ′ and ′ are obtained from the
𝑘
𝑘
1
𝑀
𝑚
graph using the equation 2 = (2𝜋)2 ( ′ + ′ 𝑁 ).
𝑓𝑘𝑘𝑀
0.0039== 9.88 × 10−5 s2
′
2
𝑘
(2𝜋)
(0.0140 − 0.0039)/5𝑚== 5.12 × 10−5 s2
′
𝑘
(2𝜋)2

Experiment

A1-9
EnglishC.4 (0.6 pt)

𝑀 /𝑘′
𝑀
9.88
=
= 1.93
=
′
𝑚
𝑚/𝑘
5.12

𝑀
= 1.93𝑚𝑀=𝑀⋅ 𝑚 = 1.93 × 0.0075 = 0.0145 kg𝑚

𝑀 = 14.5 g

𝑘′ =0.0145𝑀== 147 N/m′
𝑀 /𝑘9.88 × 10−5𝑘′ = 147 N/mExperiment

A1-10

EnglishPart D: Resonance characteristics (2.3 points)
D.1 (0.4 pt)′
𝑉AC= 0.157 V

𝐹AC = 𝐵𝐿𝐼AC = 𝐵𝐿 × 0.106 ×

√

′
2𝑉AC
= 0.696 × 0.106 ×√
2 × 0.157 = 0.0164 N

𝐹AC = 0.0164 N

D.2 (0.9 pt)
𝐴 /mm(𝑓 − 𝑓0 )2 /Hz2

1/𝐴2 /mm−2

15.88

3.0

0.0064

0.111

15.79

3.0

0.0289

0.111

15.73

2.8

0.0529

0.128

15.61

2.1

0.1225

0.227

15.49

1.9

0.2209

0.277

15.34

1.2

0.3844

0.694

15.20

1.1

0.5776

0.826

16.02

2.7

0.0036

0.137

16.14

2.1

0.0324

0.227

16.24

2.0

0.0784

0.250

16.41

1.6

0.2025

0.391

16.60

1.1

0.4096

0.826

16.81

1.0

0.7225

1.000

𝑓 /Hz

Experiment

A1-11

EnglishD.2 (cont.)

4

A /mm

3
１/√2

2
1
0
15

16
f /Hz

17

Experiment

A1-12

EnglishD.3 (1.0 pt)
Reading from the graph D.2
𝑓0 = 15.83 Hz
𝐴(𝑓0 ) = 3.0 mm
15.14 − 15.56= 0.29 Hz
2
Calculaton using Eq.(4)
Δ𝑓 =

𝑀=

𝐹AC
0.0164= 2= 0.0151 kg
8𝜋2 𝑓0 Δ𝑓𝐴(𝑓0 )8𝜋 × 15.83 × 0.29 × 0.003

𝑀 = 15.1 g

An alternative way to find 𝑀(𝑓 − 𝑓0 )2 and 1/𝐴2 are calculated in Table D.2 to use the linear relationship1
8𝜋2 𝑀 𝑓0 2=(
) ⋅ [(𝑓 − 𝑓0 )2 + (Δ𝑓)2 ] .
2𝐴𝐹AC
𝑓0 = 15.96 Hz obtained in C.2 is used.
The slope is obtained from the graph of the additional quantities or the calculation(

8𝜋2 𝑀 𝑓0 2
) = 1.31 mm−2 Hz−2 = 1.31 × 106 m−2 Hz−2 .
𝐹AC

𝑀=

√

1.31 × 106 ×√
𝐹AC
0.0164=1.31 × 106 × 2= 0.0149 kg
8𝜋2 𝑓08𝜋 × 15.96

𝑀 = 14.9 g
1.5

1/A2 /mm-2

y = ax+ba = 1.31, b = 0.11
1

0.5

0
0

0.2

0.4
0.6
2
(f-f0) /Hz2

0.8

1

Q2-1

Experiment

English (Official)

Thickness Measurements Using Birefringence (10 points)
Uncertainty analysis is not required throughout this question.
Birefringence is an optical property of a crystal that light propagates as two rays experiencing different
refractive indices. When the orthogonal crystal axes 𝑥 and 𝑦 lie in the plane of the input face of a birefringent crystal (Fig. 1), the electric field 𝐸 of linearly polarized light at normal incidence on the crystal
is decomposed into two orthogonal components 𝐸 𝑥 and 𝐸 𝑦 accompanied by refractive indices 𝑛o and𝑛e , respectively. For a crystal of thickness 𝐿, the phase shift of the 𝑥-polarized light Γ𝑥 and that of the𝑦-polarized light Γ𝑦 as they pass through the crystal are respectively given by
Γ𝑥 =

2𝜋
𝑛 𝐿,
𝜆 o

(1)

Γ𝑦 =

2𝜋
𝑛 𝐿,
𝜆 e

(2)

where 𝜆 is the wavelength of light in vacuum.

Figure 1: Vectorial decomposition of the electric field 𝐸 of linearly polarized light at normal
incidence on the surface of a birefringent crystal.
The phase difference Γ between the two rays isΓ = Γ 𝑦 − Γ𝑥 =

2𝜋
Δ𝑛𝐿,
𝜆

(3)

where
Δ𝑛 = 𝑛e − 𝑛o(4)is the birefringence. Since the electric field of light is the vectorial sum of 𝐸 𝑥 and 𝐸 𝑦 with a phase difference Γ, the light after passing through the crystal has a polarization component perpendicular to theinitial linear polarization of the incident light.
Let 𝐼∥ and 𝐼⟂ denote the intensities of the components of the light after passing through the crystal which
are parallel and perpendicular to the direction of the linear polarization of the incident light, respectively.
𝐸 in Fig. 1) is 45° with respect toHereafter the direction of the linear polarization of the incident light (𝐸the 𝑥 axis. Then the normalized intensity of the perpendicular component 𝐼Norm is given by
𝐼Norm =𝐼⟂2 Γ= sin ,
𝐼Total
2

(5)

Q2-2

Experiment

English (Official)where 𝐼Total is the total transmitted light intensity, 𝐼∥ + 𝐼⟂ .
We can design an experiment such that 𝐼Norm oscillates between 0 and 1 as we vary the wavelength of
the incident light. Let 𝜆𝑚 (𝑚 = 1, 2, 3, ⋯) be the wavelengths at which 𝐼Norm = 0; then we find the phasedifference Γ𝑚 such thatΓ𝑚 =2𝜋Δ𝑛(𝜆𝑚 )𝐿 = 2𝜋𝑚.
𝜆𝑚

(6)This equation allows us to determine the crystal thickness 𝐿 if multiple 𝜆𝑚 ’s can be measured for the
known Δ𝑛(𝜆𝑚 ).
In this experiment, you will determine the thickness of the quartz plate. Quartz is birefringent with its
refractive indices 𝑛o and 𝑛e depending on the wavelength of light in vacuum as shown in Fig. 2.

Figure 2: Wavelength dependence of the refractive indices 𝑛o and 𝑛e of quartz.
Figure 3 shows the thickness-measurement system. Shown in Figs. 4 and 5 are the optomechanical andphotonic components and devices. A white light-emitting diode (LED) is used as the light source, whichcontains a blue LED and a phosphor. When light from the blue LED is irradiated onto the phosphor,white light is emitted with a continuous spectrum. Light from this white LED is dispersed, i.e., spectrally
resolved, using the transmission diffraction grating G, and linearly polarized by the polarizer P1. Its
𝐸 in Fig. 1) is 45° off the 𝑥-axis of the quartz plate Q. The polarization component
direction of polarization (𝐸of light after passing through Q, i.e., parallel and perpendicular to the direction of polarization of P1, isselected by rotating the polarizer P2. The photodetector measures the light intensity.

Experiment

Q2-3
English (Official)

Figure 3: (a) Schematic and (b) photograph of thickness‒measurement system. LED:
white LED, S: slit, L1: collimating lens, G: transmission diffraction grating, P1: polarizer, Q:
quartz plate, P2: polarizer, L2: focusing lens, C: light-shield cylinder, PD: photodetector,
DMM: digital multimeter.

Experiment

Q2-4
English (Official)

Figure 4: Components and devices: 1(a). white LED (front view); 1(b). white LED (rearview); 2. batteries; 3. slit (S in Fig. 3); 4. LED with slit attached; 5. lens (L1, L2 in Fig. 3); 5(a)mounted lens; 5(b) lens post; 5(c) post base; 6. transmission diffraction grating (6(a) front;
6(b) rear w/ adhesive tape) on 6(c) rotation stage (G in Fig. 3); 6(d) angle readout device on
the rotation stage; 7. polarizer (P1 in Fig. 3); 8. quartz plate (Q in Fig. 3); 9. polarizer onrotation mount (P2 in Fig. 3).

Experiment

Q2-5
English (Official)

Figure 5: Components and devices (continued): 10. light‒shield cylinder with magnet (Cin Fig. 3); 11. cylinder mount; 12. photodetector (PD in Fig. 3); 13. photodetector withcylinder; 14. digital multimeter (DMM in Fig. 3); 15. short guide rail; 16. long guide rail; 17.
scale assembly; 18. white card; 19. black card; 20. anti-slip sheets; 21 & 22. light-shield box(before assembly and as assembled).

Q2-6

Experiment

English (Official)Part A. Measurement System Setup (2.3 points)
The LED output is incident on the grating surface (Fig. 6). The rotation angle 𝜃 of G for normal incidence
is defined as 0°. The counterclockwise and clockwise rotations are denoted by + and −, respectively. The
first-order diffraction angle 𝛼 is defined as illustrated. Using the groove period (or slit separation) 𝑑 ofG, the wavelength 𝜆 is given in terms of 𝜃 as
𝜆 = 𝑑 sin(𝛼 − 𝜃) + 𝑑 sin 𝜃

(7)

𝛼
𝛼
cos ( − 𝜃) .
2
2

(8)

= 2𝑑 sin

Hereafter use 𝑑 = 1.00 µm and the fixed diffraction angle 𝛼 = 40.0°.

Figure 6: The rotation angle 𝜃 of the transmission diffraction grating G and the diffraction angle 𝛼.
A.1

Calculate the longest wavelength 𝜆 that can be measured and the associated 𝜃.

0.3pt

A.2

Calculate the numeric values of 𝜃 for 𝜆 = 440 nm.

0.2pt

Setup procedures for the measurement system are as follows.
[1] Stand the scale assembly upright (17 in Fig. 5) using the pedestal (17(b)).
[2] Set two batteries on the white LED module. The ''+'' sides must face toward you.
[3] Turn on the LED.
[4] Remove the screw on the front side of the LED module. Attach the slit to the LED module with thescrew (4 in Fig. 4). Using the scale assembly, adjust the slit position to make the transmitted white light
flux brightest, and measure the height of the beam center at the exit of the slit (for the procedure [9]).
[5] Let the U-shaped open-slotted end of the long guide rail ride on that of the short one (Fig. 7(i)). Insert
the rotation axle sticking out of the bottom face of the rotation stage into the ''virtual through-hole'' madeby the guide rails (Fig. 7(ii)). Ensure free and smooth rotation of both arms about the axle referring to
Fig. 7(iii). Make sure that the long guide rail will stay on the table 0° ≤ 𝛼 ≤ 40.0°.

Experiment

Q2-7
English (Official)

Figure 7: (i) U-shaped open-slotted end of the short guide rail under that of the longguide rail making a ''virtual'' through-hole. (ii) Into the virtual hole, insert the axle sticking
out of the bottom face of the rotation stage. (iii) Top view of the rotation stage with guiderails that are free to rotate about the axle. 1. short guide rail; 2. long guide rail; 3. rotation
stage; 4. axle of the rotation stage.
[6] Align the centerline of the short guide rail with 0° on the scale of the rotation stage, and keep it inthat place. You may put an anti-slip sheet under the short guide rail.
[7] Assemble the lenses (5 in Fig. 4).
[8] Place the white LED module with the slit and the lens (L1 in Fig. 3) on the short guide rail. Adjust the
distance between the slit and L1 so that the light beam size after passing through L1 remains almost
constant, i.e., collimated, over the flight path.
[9] Using the scale assembly, measure the beam height after L1. Adjust the level of L1 by loosening thesetscrew of the post base and moving the post as necessary to keep the beam height almost the sameas that right after the slit.
[10] Align the centerline of the long guide rail with 180° on the angle scale on the rotation stage.
[11] Tweak the horizontal position of the lens mount (5(a) in Fig. 4) by loosening the setscrew and moving
it right or left. The beam center after L1 should align with the center line of the long guide rail. You may
put the scale assembly upside down over the long rail.
[12] Expose the second surface of the double-sided adhesive tape on the rear side of the transmission
diffraction grating (6(b) in Fig. 4) and affix it to the axle top of the rotation stage (6 in Fig. 4).

Experiment

Q2-8
English (Official)[13] Face the front side of the grating towards the light source, and rotate the stage so that the reflected
light enters the slit, i.e., 𝜃 = 0° (normal incidence). Record the angle 𝜃Stage of the rotation stage. It will be
used in B.1.
[14] Move the long guide rail around the axle so that 𝛼 = 40.0° (Fig. 6). Once fixed, you may place anotheranti-slip sheet thereafter to prevent accidental misalignment.
[15] Place the lens (L2 in Fig. 3) and the photodetector (PD in Fig. 3) with the cylinder mount on the longrail. To focus the diffracted light onto PD, adjust the distance between PD and L2 along the long rail, andalso the height of L2. The vertical beam diameter is thereby minimized. Check the beam diameter withthe white card. In case it is too weak to recognize with the naked eye, use the light-shield box to coverPD.
[16] Set the light-shield cylinder to the mount (13 in Fig. 5). The light shield minimizes the unwanted light
to be detected.
[17] Connect PD to the DMM. The red (black) jump wire goes to red (black) terminal. Set the multimeterto the DC voltage measurement mode.
[18] Adjust the height of L2 to maximize the DMM readings. Hereafter the intensity of light is identified
with the voltage values on the DMM.
A.3

Rotate the rotation stage and find the angle 𝜃 and the corresponding wavelength 𝜆Peak at which the blue LED spectral density is maximized, assuming that𝛼 = 40.0°. If your answer for 𝜆Peak is between 450 and 460 nm, your apparatus is properly aligned; write down 𝛼 = 40.0° on the answer sheet and continue.
Otherwise, you will have to find the true value of 𝛼. Without changing anything,including your original value for 𝜆Peak , find a corrected value for 𝛼 which would
make 𝜆Peak fall in the appropriate range. Record this 𝛼 on the answer sheet anduse it for the rest of the problem.

0.8pt[19] Set the polarizers (P1 and P2 in Fig. 3) on the long guide rail.
A.4

Set the rotation stage to the 𝜃 = −15.0° position. Watch the readings on the
DMM and find the angle 𝜑⟂ of the rotation mount of the polarizer P2 suchthat its polarization direction is perpendicular to that of the light transmitted
through the polarizer P1. From this result, find the angle 𝜑∥ of the rotation
mount of the polarizer P2 when its polarization direction is parallel to that ofthe polarizer P1.

0.3pt

A.5

Block the light through the slit by placing the black card in front of the slit. By
doing so, you can evaluate the system background, i.e., the offset of the intensity from zero. We define the light intensities 𝐼Offset ⟂ and 𝐼Offset ∥ when theangles of the rotation mount of the polarizer P2 are 𝜑⟂ and 𝜑∥ , respectively.
Measure the offsets 𝐼Offset ⟂ and 𝐼Offset ∥ . Note that 𝐼Offset ⟂ and 𝐼Offset ∥ are due
to light other than the light source. They should be eliminated by subtraction
to determine the true contribution from the light source.

0.2pt

A.6

𝐼⟂ and 𝐼∥ refer to the light intensities from the light source when the angles of
the rotation mount of the polarizer P2 are 𝜑⟂ and 𝜑∥ , respectively. Measure thelight intensities 𝐼⟂ and 𝐼∥ for 𝜃 = −15.0°.

0.5pt

Experiment

Q2-9
English (Official)Part B. Measurement of transmitted light intensities (4.7 points)
Hereafter use the values of 𝜆 calculated using the corrected value of 𝛼 in A.3 as necessary.
B.1

Place the quartz plate between polarizers P1 and P2 and measure the transmitted light intensities 𝐼⟂ and 𝐼∥ at various angles 𝜃. Your measurements should
fully cover the wavelength range of 440 nm to 660 nm. Tabulate the following
parameters: 𝜃Stage (angle readings of the rotation stage), 𝜃, 𝜆, 𝐼⟂ , 𝐼∥ , 𝐼Total =𝐼⟂ + 𝐼∥ , 𝐼Norm = 𝐼⟂ /𝐼Total . Note that when the value of 𝜃Stage increases, the valueof 𝜃 decreases with the same value, and vice versa. You do not have to use every
row of the provided table, but you should take enough data to obtain accurate
results.

2.0pt

B.2

Plot the spectrum of the white LED, i.e., 𝐼Total , versus wavelength on the graph.

1.0pt

B.3

Find the full width at half maximum Δ𝜆FWHM of the spectrum of the blue LED
built in the white LED. It is the width of a peak measured between those points
which are at half the maximum amplitude

0.2pt

B.4

Plot the spectrum of 𝐼Norm on the graph.

1.5pt

Part C. Analyses of Measured Results (3.0 points)
C.1

From the 𝐼Norm graph, find all the wavelengths at which the intensities go
through local minima. The associated order number 𝑚 according to Eq. (6)must be given below the corresponding wavelength. To determine the birefringence Δ𝑛, use the values of 𝑛o and 𝑛e given in Table 1.

1.5pt

C.2

Obtain the sample thickness 𝐿.

1.5pt

Q2-10Experiment

English (Official)

Table 1: Refractive indices 𝑛o and 𝑛e of quartz (400–700 nm).
𝜆/nm

𝑛o

𝑛e

𝜆/nm

𝑛o

𝑛e

𝜆/nm

𝑛o

𝑛e

400

1.55769

1.56725434

1.55394

1.56337467

1.551071.56041401

1.55756

1.56712435

1.55384

1.56327468

1.550991.56033402

1.55744

1.56700436

1.55374

1.56318469

1.55091

1.56025403

1.55732

1.56687437

1.55365

1.56308470

1.55084

1.56017404

1.55720

1.56674438

1.55355

1.56298471

1.55076

1.56009405

1.557071.56662439

1.55346

1.56288472

1.55068

1.56001406

1.55695

1.56649440

1.55337

1.56278473

1.55061

1.55993407

1.55684

1.56637441

1.55327

1.56269474

1.550541.55986408

1.55672

1.56625442

1.55318

1.56259475

1.55046

1.55978409

1.55660

1.56613443

1.55309

1.56250476

1.55039

1.55970410

1.556481.56601444

1.55300

1.56240477

1.550311.55963411

1.55637

1.56589445

1.55291

1.56231478

1.55024

1.55955412

1.55625

1.56577446

1.55282

1.56222479

1.550171.55948413

1.556141.56565447

1.55273

1.56213480

1.550101.55940414

1.556031.56554448

1.55264

1.56203481

1.550031.55933415

1.55592

1.56542449

1.55255

1.56194482

1.54995

1.55926416

1.55580

1.56531450

1.55247

1.56185483

1.54988

1.55918417

1.55569

1.56519451

1.55238

1.56176484

1.549811.55911418

1.55558

1.56508452

1.55229

1.56167485

1.54974

1.55904419

1.555481.56497453

1.552211.56159486

1.54967

1.55897420

1.55537

1.56485454

1.552121.56150487

1.54961

1.55890421

1.55526

1.56474455

1.55204

1.56141488

1.549541.55883422

1.55515

1.56463456

1.55195

1.56132489

1.54947

1.55875423

1.55505

1.56452457

1.55187

1.56124490

1.54940

1.55868424

1.55494

1.56442458

1.55179

1.56115491

1.54933

1.55862425

1.55484

1.56431459

1.55171

1.56107492

1.54927

1.55855426

1.55474

1.56420460

1.55162

1.56098493

1.54920

1.55848427

1.554631.56410461

1.55154

1.56090494

1.54913

1.55841428

1.55453

1.56399462

1.55146

1.56082495

1.549071.55834429

1.55443

1.56389463

1.55138

1.56073496

1.54900

1.55827430

1.55433

1.56378464

1.55130

1.56065497

1.54894

1.55821431

1.55423

1.56368465

1.551221.56057498

1.54887

1.55814432

1.554131.56358466

1.55115

1.56049499

1.548811.55807433

1.554031.56348

Q2-11

Experiment

English (Official)

𝜆/nm

𝑛o

𝑛e

𝜆/nm

𝑛o

𝑛e

𝜆/nm

𝑛o

𝑛e

500

1.54875

1.55801534

1.54678

1.55597567

1.54518

1.55432501

1.54868

1.55794535

1.54673

1.55592568

1.545141.55427502

1.54862

1.55788536

1.54667

1.55587569

1.545091.55423503

1.54856

1.55781537

1.54662

1.55581570

1.54505

1.55418504

1.54850

1.55775538

1.54657

1.55576571

1.54500

1.55414505

1.548431.55768539

1.54652

1.55570572

1.54496

1.55409506

1.54837

1.55762540

1.54647

1.55565573

1.54492

1.55405507

1.548311.55756541

1.546421.55560574

1.54487

1.55400508

1.54825

1.55749542

1.54637

1.55555575

1.54483

1.55396509

1.548191.55743543

1.54632

1.55549576

1.54479

1.55391510

1.548131.55737544

1.54627

1.55544577

1.54474

1.55387511

1.548071.55731545

1.546221.55539578

1.54470

1.55383512

1.54801

1.55725546

1.546171.55534579

1.54466

1.55378513

1.54795

1.55718547

1.546121.55529580

1.54462

1.55374514

1.54789

1.55712548

1.546071.55524581

1.54458

1.55370515

1.54783

1.55706549

1.546021.55519582

1.54453

1.55365516

1.54777

1.55700550

1.54597

1.55514583

1.54449

1.55361517

1.54772

1.55694551

1.54592

1.55509584

1.54445

1.55357518

1.54766

1.55688552

1.54587

1.55504585

1.54441

1.55352519

1.54760

1.55682553

1.54583

1.55499586

1.54437

1.55348520

1.547541.55676554

1.54578

1.55494587

1.54433

1.55344521

1.54749

1.55671555

1.54573

1.55489588

1.54429

1.55340522

1.547431.55665556

1.54568

1.55484589

1.54425

1.55336523

1.54738

1.55659557

1.545641.55479590

1.544211.55331524

1.54732

1.55653558

1.545591.55474591

1.544171.55327525

1.54726

1.55648559

1.545541.55470592

1.544131.55323526

1.547211.55642560

1.54550

1.55465593

1.54409

1.55319527

1.54715

1.55636561

1.545451.55460594

1.54405

1.55315528

1.547101.55631562

1.545411.55455595

1.54401

1.55311529

1.54705

1.55625563

1.54536

1.55451596

1.54397

1.55307530

1.54699

1.55619564

1.545311.55446597

1.54393

1.55303531

1.54694

1.55614565

1.54527

1.55441598

1.54389

1.55299532

1.54688

1.55608566

1.545221.55437599

1.54385

1.55295533

1.54683

1.55603

Q2-12

Experiment

English (Official)

𝜆/nm

𝑛o

𝑛e

𝜆/nm

𝑛o

𝑛e

𝜆/nm

𝑛o

𝑛e

600

1.54382

1.55291634

1.54260

1.55165667

1.54157

1.55059601

1.54378

1.55287635

1.54257

1.55162668

1.541541.55056602

1.54374

1.55283636

1.54254

1.55159669

1.54151

1.55053603

1.54370

1.55279637

1.54250

1.55155670

1.541481.55050604

1.54366

1.55275638

1.54247

1.55152671

1.541451.55047605

1.543631.55271639

1.54244

1.55148672

1.541431.55044606

1.54359

1.55267640

1.54241

1.55145673

1.54140

1.55041607

1.54355

1.55264641

1.54237

1.55142674

1.541371.55038608

1.54351

1.55260642

1.54234

1.55138675

1.54134

1.55035609

1.54348

1.55256643

1.54231

1.55135676

1.541311.55032610

1.543441.55252644

1.54228

1.55132677

1.541281.55029611

1.54340

1.55248645

1.54224

1.55128678

1.541251.55026612

1.54337

1.55245646

1.542211.55125679

1.541231.55023613

1.54333

1.55241647

1.54218

1.55122680

1.541201.55020614

1.54330

1.55237648

1.54215

1.55119681

1.541171.55017615

1.54326

1.55233649

1.542121.55115682

1.541141.55014616

1.543221.55230650

1.54209

1.55112683

1.541111.55011617

1.543191.55226651

1.54206

1.55109684

1.541091.55009618

1.54315

1.55222652

1.542021.55106685

1.54106

1.55006619

1.543121.55219653

1.54199

1.55102686

1.541031.55003620

1.54308

1.55215654

1.541961.55099687

1.54100

1.55000

621

1.54305

1.55211655

1.541931.55096688

1.54098

1.54997622

1.54301

1.55208656

1.541901.55093689

1.54095

1.54994623

1.54298

1.55204657

1.54187

1.55090690

1.54092

1.54992624

1.54294

1.55201658

1.54184

1.55087691

1.54090

1.54989625

1.54291

1.55197659

1.541811.55083692

1.54087

1.54986626

1.54287

1.55193660

1.54178

1.55080693

1.54084

1.54983627

1.54284

1.55190661

1.54175

1.55077694

1.540811.54980628

1.54280

1.55186662

1.54172

1.55074695

1.54079

1.54978629

1.54277

1.55183663

1.54169

1.55071696

1.54076

1.54975630

1.54274

1.55179664

1.54166

1.55068697

1.54073

1.54972631

1.54270

1.55176665

1.541631.55065698

1.54071

1.54969632

1.54267

1.55172666

1.54160

1.55062699

1.54068

1.54967633

1.54264

1.55169700

1.54066

1.54964

Experiment

A2-1
EnglishThickness Measurements Using Birefringence (10 points)
Values in black (blue) are typical (acceptable).

Part A. Measurement System Setup (2.3 points)
A.1 (0.3 pt)

𝜆 = 684 nm

𝜃 = 20.0°

A.2 (0.2 pt)

𝜃 = −30.0°, 70.0°

A.3 (0.8 pt)

𝜃 = −28.0°(−28.9° ≤ 𝜃 ≤ −27.7°or

67.7° ≤ 𝜃 ≤ 68.9°)

𝜆Peak = 458 nm(450 nm ≤ 𝜆Peak ≤ 460 nm;

𝜆Peak and 𝜃 must be consistent with Eq. (7) or (8).)

𝛼 = 40.0°

A.4 (0.3 pt)

𝜑⟂ = 90°(85° ≤ 𝜑⟂ ≤ 95°

or

265° ≤ 𝜑⟂ ≤ 275°)𝜑∥ = 0°(𝜑∥ = 𝜑⟂ + 90° or 𝜑⟂ − 90°)

ExperimentA2-2
EnglishA.5 (0.2 pt)

𝐼Offset ⟂ = 0.005 V(𝐼Offset ⟂ ≤ 0.010 V)

𝐼Offset ∥ = 0.010 V(𝐼Offset ∥ ≤ 0.020 V)

A.6 (0.5 pt)

𝐼⟂ = 0.001 V(𝐼⟂ ≤ 0.003 V)

𝐼∥ = 0.160 V(𝐼∥ ≥ 0.100 V)

Experiment

A2-3
EnglishPart B. Measurement of transmitted light intensities (4.7 points)
B.1 (2.0 pt)

𝜃Stage /degree 𝜃/degree

𝜆/nm

𝐼⟂ /mV𝐼∥ /mV

𝐼Total /mV

𝐼Norm

30.5

-31

430.5

13

26

39

0.333

30

-30.5

435.1

38

31

69

0.551

29.5

-30

439.7

83

27

110

0.755

29

-29.5

444.2

166

17

183

0.907

28.5

-29

448.8

244

21

265

0.921

28

-28.5

453.3

280

80

360

0.778

27.5

-28

457.7

267

159

426

0.627

27

-27.5

462.1

188

216

404

0.465

26.5

-27

466.5

73

223

296

0.247

26

-26.5

470.9

17

197

214

0.079

25.5

-26

475.2

12

162

174

0.069

25

-25.5

479.5

19

121

140

0.136

24.5

-25

483.7

34

71

105

0.324

24

-24.5

487.9

48

43

91

0.527

23.5

-24

492.1

61

22

83

0.735

23

-23.5

496.2

72

10

82

0.878

22.5

-23

500.3

83

4

87

0.954

22

-22.5

504.3

94

8

102

0.922

21.5

-22

508.3

97

19

116

0.836

Experiment

A2-4
EnglishB.1 (2.0 pt)(Continued)
𝜃Stage /degree 𝜃/degree

𝜆/nm

𝐼⟂ /mV𝐼∥ /mV

𝐼Total /mV

𝐼Norm

21

-21.5

512.3

92

37

129

0.713

20.5

-21

516.3

77

68

145

0.531

20

-20.5

520.1

61

90

151

0.404

19.5

-20

524.0

35

130

165

0.212

19

-19.5

527.8

18

153

171

0.105

18.5

-19

531.6

8

166

174

0.046

18

-18.5

535.3

8

167

175

0.046

17.5

-18

539.0

14

158

172

0.081

17

-17.5

542.7

32

141

173

0.185

16.5

-17

546.3

47

127

174

0.270

16

-16.5

549.9

73

99

172

0.424

15.5

-16

553.4

93

76

169

0.550

15

-15.5

556.9

112

55

167

0.671

14.5

-15

560.3

130

34

164

0.793

14

-14.5

563.7

141

20

161

0.876

13.5

-14

567.1

147

10

157

0.936

13

-13.5

570.4

148

6

154

0.961

12.5

-13

573.7

146

6

152

0.961

12

-12.5

576.9

138

10

148

0.932

Experiment

A2-5
EnglishB.1 (2.0 pt)(Continued)
𝜃Stage /degree 𝜃/degree

𝜆/nm

𝐼⟂ /mV𝐼∥ /mV

𝐼Total /mV

𝐼Norm

11.5

-12

580.1

127

17

144

0.882

11

-11.5

583.2

114

26

140

0.814

10.5

-11

586.3

97

38

135

0.719

10

-10.5

589.4

80

50

130

0.615

9.5

-10

592.4

67

60

127

0.528

9

-9.5

595.4

54

69

123

0.439

8.5

-9

598.3

41

76

117

0.350

8

-8.5

601.1

31

81

112

0.277

7.5

-8

604.0

22

87

109

0.202

7

-7.5

606.8

15

89

104

0.144

6.5

-7

609.5

8

91

99

0.081

6

-6.5

612.2

6

91

97

0.062

5.5

-6

614.8

4

89

93

0.043

5

-5.5

617.4

3

85

88

0.034

4.5

-5

620.0

4

81

85

0.047

4

-4.5

622.5

5

74

79

0.063

3.5

-4

624.9

7

69

76

0.092

3

-3.5

627.3

10

63

73

0.137

2.5

-3

629.7

12

57

69

0.174

Experiment

A2-6
EnglishB.1 (2.0 pt)(Continued)
𝜃Stage /degree 𝜃/degree

𝜆/nm

𝐼⟂ /mV𝐼∥ /mV

𝐼Total /mV

𝐼Norm

2

-2.5

632.0

15

51

66

0.227

1.5

-2

634.2

18

44

62

0.290

1

-1.5

636.4

21

37

58

0.362

0.5

-1

638.6

23

32

55

0.418

0

-0.5

640.7

25

30

55

0.455

-0.5

0

642.8

27

26

53

0.509

-1.5

1

646.8

29

18

47

0.617

-2.5

2

650.6

31

13

44

0.705

-3.5

3

654.2

32

9

41

0.780

-4.5

4

657.5

32

6

38

0.842

-5.5

5

660.7

31

4

35

0.886

-6.5

6

663.7

30

3

33

0.909

-7.5

7

666.5

28

2

30

0.933

-8.5

8

669.1

27

2

29

0.931

-9.5

9

671.5

26

2

28

0.929

-10.5

10

673.6

24

2

26

0.923

-11.5

11

675.6

23

2

25

0.920

-13.5

13

678.9

20

2

22

0.909

-15.5

15

681.4

18

3

21

0.857

Experiment

A2-7
EnglishB.2 (1.0 pt)

!!
""!
"!!
#"!
#!!

/.-',+*)('

$"!
$!!
%"!
%!!
&"!
&!!
"!
!
#%! ##! # ! #1! "!! "%! "#! " ! "1!

!!

2+34,456*7'l-5.
B.3 (0.2 pt)

Δ𝜆FWHM = 25 nm(Δ𝜆FWHM ≤ 40 nm)

%!

#!

!

1! 0!!

Experiment

A2-8
EnglishB.4 (1.5 pt)

!"
"!#
"!$
"!%
"!&
/.-,+

"!'
"!(
"!)
"!*
"!
"!"
(*" ((" (&" ($" '"" '*" '(" '&" '$" &"" &*" &(" &&" &$" %""0123435678+l95/

ExperimentA2-9
EnglishPart C. Analyses of Measured Results (3.0 points)
C.1 (1.5 pt)

𝜆 = 473 nm, 534 nm, 617 nm(455 nm < 𝜆 < 479 nm,
𝑚 = 8,

7,

513 nm < 𝜆 < 539 nm,

6

C.2 (1.5 pt)

𝐿 = 407 𝜇m(390 𝜇m < 𝐿 < 410 𝜇m)

590 nm < 𝜆 < 620 nm)

Theoretical
Examination

Theory

G0-1
English (Official)

General Instructions
Failure to comply with one or more of the following conditions may result in disqualification.
The exam is worth a total of 30 points and lasts five hours.
When to start and finish up the examination and when 15 minutes remain before the end of the examination will be indicated by your Invigilator.
Do not open the envelopes until instructed to do so.
The following items are provided for your use on the table: (1) a ballpoint pen, (2) a mechanical pencil,(3) a plastic eraser, (4) a scale ruler, (5) a scientific calculator, and (6) a digital table clock.
During the exam:• Use the ballpoint pen provided. If you use the mechanical pencil to draft your notes, figures, tables,and graphs, never fail to trace the outlines of the final version with the ballpoint pen.
• Use the dedicated sheets labeled A for your final answers. Fill in appropriate sections with youranswers and necessary observations. Draw graphs as required. Cross out any unneeded answers.
• Blank working sheets labeled W are provided for drafting. Use the designated ones. Cross out any
unneeded answers and rough work that do not need to be graded. Use only the front face of each
sheet and keep the margin outside the border clean.
• Additional working sheets labeled Z are available upon request. Raise the "Help" flag and let theInvigilator know.
• Keep your answers concise and legible. Use equations, logical operators, symbols, and sketches
that best convey your thoughts. Avoid being lengthy and wordy as the markers may not be multilingual.
• Uncertainty quantification is not required unless otherwise specified.
• You will be video-recorded for fairness and security purposes. Do not leave your booth without
permission. If you need a washroom break or any other assistance, raise the flag(s) marked "Toilet","Water", or "Help".
At the end of the exam:• Stop writing immediately when the end of the exam is announced.
• Put all the sheets in the windowed envelope for each question. Organize them faceup in the following order: cover sheet on top, question sheets (Q), answer sheets (A), working sheets (W), andadditional working sheets (Z), if any. Arrange them according to their page numbers. In the final
check, make sure that your ID, name, and seat number on the cover sheet are visible through thewindow. Leave only the General Instructions (yellow sheets stapled) on the table.
• Your Invigilator will let you know when you can leave. You may take the remaining items withyou, for example, the ballpoint pen, the mechanical pencil, the plastic eraser, the scale ruler, thescientific calculator, the digital table clock, the bottle of drinking water, and snacks.

Theory

G0-2
English (Official)

Physical Constants
Below is the list of physical constants you might use in your solution in addition to the quantities givenin the body text.

Physical constantNotation

Numerical value

Speed of light in vacuum𝑐299 792 458 m/s

Vacuum permeability (magnetic constant)

𝜇01.256 637 062 12(19) × 10−6 N/A2 ;[1 N/A2 = 1 V ⋅ s/(A ⋅ m)]

Vacuum permittivity (electric constant)

𝜀08.854 187 8128(13) × 10−12 F/m;
[1 F/m = 1 A ⋅ s/(V ⋅ m)]

Elementary charge𝑒1.602 176 634 × 10−19 C ;[1 C = 1 A ⋅ s]Electron mass𝑚e

9.109 383 7015(28) × 10−31 kg

Newtonian constant of gravitation

𝐺

6.674 30(15) × 10−11 m3 /(kg · s2 )Avogadro constant𝑁A

6.022 140 76 × 1023 mol−1

Molar gas constant𝑅

8.314 462 618 … J/(K · mol)Boltzmann constant𝑘

1.380 649 × 10−23 J/K

Stefan–Boltzmann constant𝜎

5.670 374 419 …×10−8 W/(m2 · K4 )Planck constantℎ6.626 070 15 × 10−34 J · s

Reduced Planck constantħ = ℎ/(2𝜋)1.054 571 817 … × 10−34 J · s

Q1-1

TheoryEnglish (Official)

Characterization of Soil Colloids (10 points)
Colloidal science is useful to characterize soil particles because many of them can be regarded as colloidal
particles of micrometer size. For example, Brownian motion (random motion of colloidal particles) canbe used to measure particle sizes.

Part A. Motions of colloidal particles (1.6 points)
We analyze the one-dimensional Brownian motion of a colloidal particle with mass 𝑀 . The equation of
motion for its velocity 𝑣(𝑡) reads:(1)

𝑀 𝑣 ̇ = −𝛾𝑣(𝑡) + 𝐹 (𝑡) + 𝐹ext (𝑡),where 𝛾 is the friction coefficient, 𝐹 (𝑡) is a force due to random collisions with water molecules, and𝐹ext (𝑡) is an external force. In Part A, we assume 𝐹ext (𝑡) = 0.
A.1

Consider that a water molecule collides with the particle at 𝑡 = 𝑡0 , giving impulse
𝐼0 , and 𝐹 (𝑡) = 0 afterward. If 𝑣(𝑡) = 0 before the collision, 𝑣(𝑡) = 𝑣0 𝑒−(𝑡−𝑡0 )/𝜏 for𝑡 > 𝑡0 . Determine 𝑣0 and 𝜏 , using 𝐼0 and necessary parameters in Eq.(1).

0.8pt

In the following, you may use 𝜏 in your answers.
A.2

Actually, water molecules collide with the particle one after another. Suppose
the 𝑖th collision gives the impulse 𝐼𝑖 at time 𝑡𝑖 and determine 𝑣(𝑡) on condition
that 𝑡 > 0 and 𝑣(0) = 0. Also give the inequality specifying the range of 𝑡𝑖 thatneeds to be considered for a given 𝑡. In the answer sheet, it is not necessary to
specify this range in the expression for 𝑣(𝑡).

0.8ptPart B. Effective equation of motion (1.8 points)
Results so far imply that particle velocities 𝑣(𝑡) and 𝑣(𝑡′ ) may be regarded as uncorrelated random quantities if |𝑡 − 𝑡′ | ≫ 𝜏 . On this basis, we introduce a theoretical model to approximately describe the onedimensional Brownian motion, where the velocity changes randomly at each time interval 𝛿 (≫ 𝜏 ), i.e.,𝑣(𝑡) = 𝑣𝑛(2)(𝑡𝑛−1 < 𝑡 ≤ 𝑡𝑛 ),with 𝑡𝑛 = 𝑛𝛿 (𝑛 = 0, 1, 2, ⋯) and a random quantity 𝑣𝑛 . It satisfies⟨𝑣𝑛 ⟩ = 0,⟨𝑣𝑛 𝑣𝑚 ⟩ = {𝐶0(𝑛 = 𝑚),(𝑛 ≠ 𝑚),(3)

with a parameter 𝐶 depending on 𝛿. Here ⟨𝑋⟩ indicates the expectation value of 𝑋. That is, if you draw
random numbers 𝑋 infinite times, the mean will be ⟨𝑋⟩.
Now we consider the particle displacement Δ𝑥(𝑡) = 𝑥(𝑡) − 𝑥(0) for 𝑡 = 𝑁 𝛿 with an integer 𝑁 .
B.1

Determine ⟨Δ𝑥(𝑡)⟩ and ⟨Δ𝑥(𝑡)2 ⟩ using 𝐶, 𝛿, and 𝑡.

1.0pt

Q1-2

TheoryEnglish (Official)

B.2

The quantity ⟨Δ𝑥(𝑡)2 ⟩ is called the mean square displacement (MSD). It is a characteristic observable of the Brownian motion, which corresponds to the limitingcase 𝛿 → 0. From this, we can show 𝐶 ∝ 𝛿 𝛼 and ⟨Δ𝑥(𝑡)2 ⟩ ∝ 𝑡𝛽 . Determine thevalues of 𝛼 and 𝛽.

0.8pt

Part C. Electrophoresis (2.7 points)
Here we discuss electrophoresis, i.e., transport of charged particles by an electric field. Suspension ofcolloidal particles with mass 𝑀 and charge 𝑄 (> 0) is put in a narrow channel with a cross-section 𝐴(Fig.1(a)). We ignore the interaction between particles, effects of the wall, the fluid, the ions therein, andgravity.

Fig.1: Setting for Part C.
By applying a uniform electric field 𝐸 in the 𝑥-direction, particles are transported and their concentration𝑛(𝑥) (particle number per unit volume) becomes non-uniform (Fig.1(b)). When 𝐸 is removed, this nonuniformity gradually disappears. This is due to Brownian motion of particles. If 𝑛(𝑥) is not uniform, thenumbers of right-going and left-going particles may differ (Fig.1(c)). This generates a particle flux 𝐽𝐷 (𝑥),the mean number of particles flowing at 𝑥 along the 𝑥-axis per unit cross-sectional area and unit time.
This flux is known to satisfy
𝐽𝐷 (𝑥) = −𝐷

𝑑𝑛
(𝑥),
𝑑𝑥

(4)

where 𝐷 is called the diffusion coefficient.
Now let's assume, for simplicity, that half of the particles have velocity +𝑣 and the other half have velocity−𝑣. Let 𝑁+ (𝑥0 ) be the number of particles with velocity +𝑣 that cross 𝑥0 from left to right per unit crosssectional area and unit time. For particles with velocity +𝑣 to cross 𝑥0 in the time interval 𝛿, they should
be in the shaded region of Fig.1(c). Since 𝛿 is small, we have 𝑛(𝑥) ≃ 𝑛(𝑥0 ) + (𝑥 − 𝑥0 ) 𝑑𝑛𝑑𝑥 (𝑥0 ) in this region.
C.1

Express 𝑁+ (𝑥0 ) using necessary quantities from 𝑣, 𝛿, 𝑛(𝑥0 ), and 𝑑𝑛𝑑𝑥 (𝑥0 ).

0.5pt

We define 𝑁− (𝑥0 ) as the counterpart of 𝑁+ (𝑥0 ) for the velocity −𝑣. With this, we have 𝐽𝐷 (𝑥0 ) = ⟨𝑁+ (𝑥0 ) −𝑁− (𝑥0 )⟩. According to Eq.(3), we have ⟨𝑣2 ⟩ = 𝐶.
C.2

Determine 𝐽𝐷 (𝑥0 ) using necessary quantities from 𝐶, 𝛿, 𝑛(𝑥0 ), and 𝑑𝑛𝑑𝑥 (𝑥0 ). Using
this and Eq.(4), express 𝐷 in terms of 𝐶 and 𝛿, and ⟨Δ𝑥(𝑡)2 ⟩ in terms of 𝐷 and 𝑡.

0.7pt

Q1-3

TheoryEnglish (Official)

Now we discuss the effect of osmotic pressure Π. It is given by Π = 𝑁𝑛 𝑅𝑇 = 𝑛𝑘𝑇 with the Avogadro𝐴
constant 𝑁𝐴 , the gas constant 𝑅, temperature 𝑇 , and the Boltzmann constant 𝑘 = 𝑁𝑅 . Let us consider𝐴
the non-uniform concentration formed under the electric field 𝐸 (Fig.1(b)). Since 𝑛(𝑥) depends on 𝑥, so
does Π(𝑥). Then the forces due to Π(𝑥) and Π(𝑥+Δ𝑥) must be balanced with the total force from the field
𝐸 acting on the particles (Fig.2). Here we consider small Δ𝑥, so that 𝑛(𝑥) can be regarded as constantover this range, while 𝑛(𝑥 + Δ𝑥) − 𝑛(𝑥) ≃ Δ𝑥 𝑑𝑛𝑑𝑥 (𝑥).

Fig.2: Force balance.
C.3

Express 𝑑𝑛
𝑑𝑥 (𝑥) using 𝑛(𝑥), 𝑇 , 𝑄, 𝐸, and 𝑘.

0.5pt

Let us discuss the balance of the flux now. Besides the flux 𝐽𝐷 (𝑥) due to the Brownian motion, there isalso a flux due to the electric field, 𝐽𝑄 (𝑥). It is given by(5)

𝐽𝑄 (𝑥) = 𝑛(𝑥)𝑢,where 𝑢 is the terminal velocity of particles driven by the field.
C.4

To determine 𝑢, we use Eq.(1) with 𝐹ext (𝑡) = 𝑄𝐸. Since 𝑣(𝑡) is fluctuating, we
consider ⟨𝑣(𝑡)⟩. Assuming ⟨𝑣(0)⟩ = 0 and using ⟨𝐹 (𝑡)⟩ = 0, evaluate ⟨𝑣(𝑡)⟩ andobtain 𝑢 = lim𝑡→∞ ⟨𝑣(𝑡)⟩.

0.5pt

C.5

The flux balance reads 𝐽𝐷 (𝑥) + 𝐽𝑄 (𝑥) = 0. Express the diffusion coefficient 𝐷 interms of 𝑘, 𝛾, and 𝑇 .

0.5pt

Part D. Mean square displacement (2.4 points)
Suppose we observed the Brownian motion of an isolated, spherical colloidal particle with radius 𝑎 =5.0 𝜇m in water. Figure 3 shows the histogram of displacements Δ𝑥 measured in the 𝑥-direction at every
interval Δ𝑡 = 60 s. The friction coefficient is given by 𝛾 = 6𝜋𝑎𝜂 with water viscosity 𝜂 = 8.9 × 10−4 Pa ⋅ s
and the temperature was 𝑇 = 25 ∘ C.

Q1-4

TheoryEnglish (Official)

Fig.3: Histogram of displacements.
D.1

Estimate the value of 𝑁𝐴 without using the fact that it is the Avogadro constant,
up to two significant digits from the data in Fig.3. The gas constant is 𝑅 =8.31 J/K ⋅ mol. Do not use the value of the Boltzmann constant 𝑘 given in General
Instructions. As for the Avogadro constant, you might obtain a value different
from that in General Instructions.

1.0pt

Now we extend the model in Part B to describe the motion of a particle with charge 𝑄 under an electricfield 𝐸. The particle velocity 𝑣(𝑡) considered in Eq.(2) should be replaced by 𝑣(𝑡) = 𝑢 + 𝑣𝑛 (𝑡𝑛−1 < 𝑡 ≤ 𝑡𝑛 )with 𝑣𝑛 satisfying Eq. (3) and 𝑢 being the terminal velocity considered in Eq.(5).
D.2

Express the MSD ⟨Δ𝑥(𝑡)2 ⟩ in terms of 𝑢, 𝐷, and 𝑡. Obtain approximate powerlaws for small 𝑡 and large 𝑡, as well as the characteristic time 𝑡∗ where this change
occurs. Draw a rough graph of MSD in a log-log plot, indicating the approximate
location of 𝑡∗ .

0.8pt

Next, we consider swimming microbes (Fig.4(a)), in one dimension for simplicity (Fig.4(b)). These arespherical particles with radius 𝑎. They swim at velocity either +𝑢0 or−𝑢0 , the sign chosen randomly at
every time interval 𝛿0 without correlation. The observed motion is a combination of displacements due
to swimming and those due to the Brownian motion of a spherical particle.

Fig.4: (a) Motion of microbes. (b) Its one-dimensional version.

Q1-5

TheoryEnglish (Official)

D.3

Figure 5 displays the MSD ⟨Δ𝑥(𝑡)2 ⟩ of those microbes, showing different powerlaws for small, large, and intermidiate 𝑡, as indicated by dashed lines. Obtain
the power law for each time range and express it using necessary quantities
from 𝐷, 𝑢0 , 𝛿0 , and 𝑡.

0.6pt

Fig.5: Mean square displacement of the microbes.

Part E. Water purification (1.5 points)
Here we discuss the purification of water including colloid-like soil particles, by adding electrolytes tocoagulate them. Particles interact through van der Waals force and electrostatic force, the latter including effects of both surface charges and the surrounding layer of oppositely charged ions (such ions andtheir layer are called counter-ions and the electric double layer, respectively; see Fig.6(a)). As a result,the interaction potential for particle distance 𝑑 (Fig.6(b)) is given by
𝑈 (𝑑) = −𝐴 𝐵𝜖(𝑘𝑇 )2 −𝑑/𝜆
+
𝑒
,
𝑑
𝑞2

(6)

where 𝐴 and 𝐵 are positive constants, 𝜖 is the dielectric constant of water, and 𝜆 is the thickness of theelectric double layer. Assuming that charges of ions are ±𝑞, we have

𝜆=√where 𝑐 is the molar concentration of ion.

𝜖𝑘𝑇,
2𝑁𝐴 𝑞 2 𝑐

(7)

Theory

Q1-6
English (Official)

Fig.6: (a) Surface charges of colloidal particles and counter-ions. (b) Definition of the distance𝑑.
E.1

Addition of sodium chloride (NaCl) to the suspension causes colloidal particles
to coagulate. Determine the lowest concentration 𝑐 of NaCl necessary for coagulation. It is sufficient to consider two particles without thermal fluctuations,
i.e., 𝐹 (𝑡) = 0 in Eq.(1), and assume that the terminal velocity for the given potential force is reached instantaneously.

1.5pt

Q2-1

TheoryEnglish (Official)

Neutron Stars (10 points)
We discuss the stability of large nuclei and estimate the mass of neutron stars theoretically and experimentally.

Part A. Mass and stability of nuclei (2.5 points)
The rest-energy of a nucleus 𝑚(𝑍, 𝑁 )𝑐2 consisting of 𝑍 protons and 𝑁 neutrons is smaller than the sum ofrest-energies of protons and neutrons, hereafter called nucleons, by the binding energy 𝐵(𝑍, 𝑁 ), where𝑐 is the speed of light in vacuum. Ignoring minor corrections, we can approximate the binding energy
consisting of the volume term with 𝑎𝑉 , the surface term with 𝑎𝑆 , the Coulomb energy term with 𝑎𝐶 , andthe symmetry energy term with 𝑎sym in the following way.
𝑚(𝑍, 𝑁 )𝑐2 = 𝐴𝑚𝑁 𝑐2 − 𝐵(𝑍, 𝑁 ),𝐵(𝑍, 𝑁 ) = 𝑎𝑉 𝐴 − 𝑎𝑆 𝐴2/3 − 𝑎𝐶

𝑍2
(𝑁 − 𝑍)2
−
𝑎
,
sym
𝐴
𝐴1/3

(1)

where 𝐴 = 𝑍 + 𝑁 is the mass number and 𝑚𝑁 is the nucleon mass. In the calculation, use 𝑎𝑉 ≈ 15.8 MeV,𝑎𝑆 ≈ 17.8 MeV, 𝑎𝐶 ≈ 0.711 MeV, and 𝑎sym ≈ 23.7 MeV (MeV = 106 electron volts).
A.1

Under the condition of 𝑍 = 𝑁 , determine 𝐴 for maximizing the binding energy
per nucleon, 𝐵/𝐴.

0.9pt

A.2

Under the condition of fixed 𝐴, the atomic number of the most stable nucleus
𝑍 ∗ is determined by maximizing 𝐵(𝑍, 𝐴 − 𝑍). For 𝐴 = 197, calculate 𝑍 ∗ using
Eq. (1).

0.9pt

A.3

A nucleus having large 𝐴 breaks up into lighter nuclei through fission in order tominimize the total rest-mass energy. For simplicity, we consider one of multiple
ways to break a nucleus with (𝑍, 𝑁 ) into two equal nuclei, which occurs when
the following energy relation holds,

0.7pt

𝑚(𝑍, 𝑁 )𝑐2 > 2𝑚(𝑍/2, 𝑁 /2)𝑐2 .
When this relation is written as
𝑍 2 /𝐴 > 𝐶fission

𝑎𝑆
,
𝑎𝐶

obtain 𝐶fission up to two significant digits.

Part B. Neutron star as a gigantic nucleus (1.5 points)
For large nuclei with a large enough mass number 𝐴 > 𝐴𝑐 with a threshold 𝐴𝑐 , these nuclei stay stableagainst nuclear fission because of the sufficiently large binding energy due to gravity.

Q2-2

TheoryEnglish (Official)

B.1

We assume that 𝑁 = 𝐴 and 𝑍 = 0 is realized for sufficiently large 𝐴 and Eq.
(1) continues to hold with the addition of the gravitational binding energy. The
binding energy due to gravity is
𝐵grav =

1.5pt

3 𝐺𝑀 2,
5 𝑅

where 𝑀 = 𝑚𝑁 𝐴 and 𝑅 = 𝑅0 𝐴1/3 with 𝑅0 ≃ 1.1 × 10−15 m = 1.1 fm are the massand the radius of the nucleus, respectively.
For 𝐵grav = 𝑎grav 𝐴5/3 , obtain 𝑎grav in the MeV unit up to the first significant digit.
Then, ignoring the surface term, estimate 𝐴𝑐 up to the first significant digit. In
the calculation, use 𝑚𝑁 𝑐2 ≃ 939 MeV and 𝐺 = ħ𝑐/𝑀𝑃2 where 𝑀𝑃 𝑐2 ≃ 1.22 ×
1022 MeV and ħ𝑐 ≃ 197 MeV ⋅ fm.

Part C. Neutron star in a binary system (6.0 points)
Some neutron stars are pulsars regularly emitting electromagnetic waves, which we call "light" for simplicity here, at a constant period. Neutron stars often make binary systems with a White Dwarf. Let us
consider the star configuration shown in Fig. 1, where a light pulse from a neutron star N to the EarthE passes near a White Dwarf W of the binary system. Measuring these pulses influenced by the star's
gravity leads to an accurate estimation of the mass of W as explained below, resulting in the estimationof the mass of N.

Fig. 1: Configurations with the 𝑥-axis along the line connecting N and E. (a) for 𝑥𝑁 < 0 and (b)for 𝑥𝑁 > 0.

Q2-3

TheoryEnglish (Official)

C.1

As shown in the figure below, under the constant gravitational acceleration 𝑔
we place two levels I and II with the height difference Δℎ(> 0). Set the identicalclocks at I, II, and 𝐹 , the free-falling system, denoted by clock-I, clock-II, andclock-𝐹 , respectively.

1.0pt

Set-up of the thought experiment.
We assume that an observer sits with clock-𝐹 , and initially 𝐹 is placed at thesame height as that of clock-I and its velocity is zero. Since the clocks are identical, they register equal time intervals, Δ𝜏𝐹 = Δ𝜏I . Then, we let 𝐹 fall freely, andwork in the frame of 𝐹 , which is considered to be inertial. In this frame, clockII passes by clock-𝐹 with velocity 𝑣, so that the time dilation of clock-II can be
determined by the Lorentz transformation. When time Δ𝜏I elapses on clock-𝐹 ,time Δ𝜏II elapses on clock-II.
Determine Δ𝜏II in terms of Δ𝜏I up to the first order in Δ𝜙/𝑐2 , where Δ𝜙 = 𝑔Δℎ isa difference of the gravitational potential, i.e., the gravitational potential energy
per unit mass.
C.2

Under the gravitational potential 𝜙, time delays change the effective speed oflight, 𝑐eff , observed at the infinity, though the local speed of light is 𝑐. When𝜙(𝑟 = ∞) = 0, 𝑐eff can be given up to the first order in 𝜙/𝑐2 as𝑐eff ≈ (1 +

2𝜙
)𝑐
𝑐2

including the effect of space distortion, which was not featured in C.1. We notethat the light path can be approximated as a straight line.
As shown in Fig. 1 (a), we take the 𝑥-axis along the light path from the neutronstar N to the Earth E and place 𝑥 = 0 at the point where the White Dwarf W is
the closest to the light path. Let 𝑥𝑁 (< 0) be the 𝑥-coordinate of N, 𝑥𝐸 (> 0) bethat of E, and 𝑑 be the distance between W and the light path.
Estimate the changes of the arrival time Δ𝑡 of the light from N to E caused by
the White Dwarf with mass 𝑀WD and evaluate the answer in a simple form disregarding higher order terms of the following small quantities: 𝑑/|𝑥𝑁 | ≪ 1,
𝑑/𝑥𝐸 ≪ 1, and 𝐺𝑀WD /(𝑐2 𝑑) ≪ 1. If necessary, use the following formula.
√1𝑥2 + 𝑑2 + 𝑥𝑑𝑥= log( √) + 𝐶.
∫√
2𝑥2 + 𝑑 2
𝑥2 + 𝑑2 − 𝑥( log is the natural logarithm)

1.8pt

Q2-4

TheoryEnglish (Official)

C.3

As shown below, in a binary star system N and W are assumed to be moving incircular orbits with zero eccentricity around the center of mass 𝐺 on the orbit
plane. Let 𝜀 be the orbital inclination angle measured from the orbit plane tothe line directed toward E from 𝐺, and let 𝐿 be the length between N and W
and 𝑀WD be the mass of the White Dwarf. In the following, we assume 𝜀 ≪ 1.

1.8pt

Binary star system.
We observe light pulses from N on E far away from N. The light path to E varies
with time depending on the configuration of N and W. The delay in the timeinterval of arriving pulses on E has the maximum value Δ𝑡max for 𝑥𝑁 ≃ −𝐿
and the minimum value Δ𝑡min for 𝑥𝑁 ≃ 𝐿 (see Fig. 1 (b) for the configuration).
Calculate Δ𝑡max − Δ𝑡min in a simple form disregarding higher order terms ofsmall quantities as done in C.2. We note that the delays due to gravity fromstellar objects other than W are assumed to cancel out in Δ𝑡max − Δ𝑡min .
C.4

The below figure shows the observed time delays as a function of the orbital
phase 𝜑 for the binary star system with 𝐿 ≈ 6 × 106 km and cos 𝜀 ≈ 0.99989.
Estimate 𝑀WD in terms of the solar mass 𝑀⊙ and show the results for 𝑀WD /𝑀⊙
up to the first significant digit. Here the approximate relation, 𝐺𝑀⊙ /𝑐3 ≈ 5 𝜇s,
can be used.

0.8pt

Observed time delays Δ𝑡 as a function of the orbital phase 𝜑 (see thefigure in C.3) to locate N and W on the orbits.

C.5

In the binary system of neutron stars, two stars release energy and angularmomentum by emitting gravitational waves and eventually collide to merge.
For simplicity, let us consider only a circular motion with the radius 𝑅 and theangular velocity 𝜔 and then 𝜔 = 𝜒𝑅𝑝 holds with the constant 𝜒 depending onneither 𝜔 nor 𝑅 if relativistic effects are ignored. Determine the value for 𝑝.

0.4pt

Q2-5

TheoryEnglish (Official)

C.6

The amplitude of the emitted gravitational wave from the binary system in C.5 is
proportional to 𝑅2 𝜔2 . Figure below qualitatively shows four different temporalprofiles of the observed gravitational waves before the two-star collision. Selectthe most appropriate profile from (a) to (d).

Observed data profiles of gravitational waves.

0.2pt

Solutions to Theory Problems

S1‒1
Theory Problem 1: Characterization of Soil Colloids (10 points)
Part A. Analysis of motions of colloidal particles (1.6 points)
A.1

The relation between the impulse and the momentum change is given by 𝑀 𝑣0 = 𝐼0 . Therefore,
𝑣0 =

𝐼0
.
𝑀

(S1.1)For the situation considered here, the equation of motion reads(S1.2)

𝑀 𝑣 ̇ = −𝛾𝑣(𝑡).
Substituting the form of the solution given in the question sheet, 𝑣(𝑡) = 𝑣0 𝑒−(𝑡−𝑡0 )/𝜏 , we obtain
𝜏=

A.1

𝑀
.
𝛾

(S1.3)

0.8 pt𝐼𝑣0 = 0𝑀
𝑀𝜏=𝛾

A.2 Thanks to the linearity of Eq. (S1.2), we can use the superposition principle, which tells us that 𝑣(𝑡) is
given by the sum of solutions for single collision events that occur before time 𝑡. This immediately gives
the solution as𝑣(𝑡) = ∑𝑖𝐼𝑖 −(𝑡−𝑡𝑖 )/𝜏𝑒,
𝑀(S1.4)

where the sum is taken in the range of 𝑖 that satisfies 0 < 𝑡𝑖 < 𝑡.
It is also not difficult to figure out this superposition principle, by considering the effect of a single collision as well as the velocity change between two consecutive collisions. From A.1, it is straightforward toshow that the velocity right after the 𝑖th collision is given by𝑣(𝑡𝑖 ) = 𝑣0 (𝑡𝑖 ) +𝐼𝑖,
𝑀(S1.5)

where 𝑣0 (𝑡𝑖 ) is the velocity right before the collision. Also, since there is no collision during 𝑡𝑖 < 𝑡 < 𝑡𝑖+1 ,we have𝑣(𝑡) = (𝑣0 (𝑡𝑖 ) +𝐼𝑖) 𝑒−(𝑡−𝑡𝑖 )/𝜏 .
𝑀(S1.6)

In particular,𝑣0 (𝑡𝑖+1 ) = (𝑣0 (𝑡𝑖 ) +𝐼𝑖) 𝑒−(𝑡𝑖+1 −𝑡𝑖 )/𝜏 .
𝑀(S1.7)

Therefore, with 𝑣0 (𝑡1 ) = 0, we obtain𝑖−1

𝐼𝑗 −(𝑡 −𝑡 )/𝜏
𝑒 𝑖 𝑗
𝑀
𝑗=1

(S1.8)𝑣0 (𝑡𝑖 ) = ∑1

Solutions to Theory Problems

S1‒2
and, for 𝑡𝑖 < 𝑡 < 𝑡𝑖+1 ,𝑖

𝐼𝑗 −(𝑡−𝑡 )/𝜏
𝑗
𝑒
.
𝑀
𝑗=1

(S1.9)

𝑣(𝑡) = ∑This is equivalent to Eq. (S1.4).
A.2

𝐼𝑣(𝑡) = ∑ 𝑖 𝑒−(𝑡−𝑡𝑖 )/𝜏𝑀𝑖
the inequality specifying the range of 𝑡𝑖 that needs to be considered:
0 < 𝑡𝑖 < 𝑡

0.8 ptPart B. Effective equation of motion (1.8 points)
B.1

From the definition of the model, we have𝑁

(S1.10)Δ𝑥(𝑡) = ∑ 𝑣𝑛 𝛿.
𝑛=1

Taking the average and using ⟨𝑣𝑛 ⟩ = 0, we obtain(S1.11)⟨Δ𝑥(𝑡)⟩ = 0.

For the mean square displacement, computing the square of Eq. (S1.10) and taking the average, we
obtain𝑁

𝑁(S1.12)⟨Δ𝑥(𝑡)2 ⟩ = ∑ ∑⟨𝑣𝑚 𝑣𝑛 ⟩𝛿 2 .
𝑚=1 𝑛=1

Using ⟨𝑣𝑚 𝑣𝑛 ⟩ = 𝐶 for 𝑛 = 𝑚 and 0 otherwise, we find𝑁

(S1.13)⟨Δ𝑥(𝑡)2 ⟩ = ∑ 𝐶𝛿 2 = 𝑁 𝐶𝛿 2 .
𝑛=1

Since 𝑁 𝛿 = 𝑡, we obtain(S1.14)⟨Δ𝑥(𝑡)2 ⟩ = 𝐶𝛿𝑡.

B.1

1.0 pt⟨Δ𝑥(𝑡)⟩ = 0⟨Δ𝑥(𝑡)2 ⟩ = 𝐶𝛿𝑡

B.2
As described in the question sheet, the mean square displacement ⟨Δ𝑥(𝑡)2 ⟩ is a characteristic
observable of the Brownian motion, which of course takes a finite value for a given 𝑡. For the model
considered here, we have Eq. (S1.14), but we need to consider the limit 𝛿 → 0 to describe the Brownian
motion in this model. This requires that 𝐶𝛿 remains finite, so that 𝐶 ∝ 𝛿 −1 . It also follows that ⟨Δ𝑥(𝑡)2 ⟩ ∝ 𝑡.
▷ Note: The continuous time limit 𝛿 → 0 of the present model corresponds to what is called the overdamped Langevin equation. This reads, in the absence of external force as considered here,𝛾𝑑𝑥= 𝜉(𝑡)
𝑑𝑡(S1.15)2

Solutions to Theory Problems

S1‒3
with a Gaussian noise 𝜉(𝑡) that satisfies⟨𝜉(𝑡)⟩ = 0,

(S1.16)⟨𝜉(𝑡)𝜉(𝑡′ )⟩ = 2𝐷𝛿(𝑡 − 𝑡′ )with the diffusion coefficient 𝐷. Here, 𝛿(𝑡) (not to confuse with 𝛿 in the problem) is called the delta𝑏function, which satisfies 𝛿(𝑡) = 0 for 𝑡 ≠ 0 and 𝛿(0) = ∞ but ∫𝑎 𝛿(𝑡)𝑑𝑡 = 1 for any 𝑎 < 0 and 𝑏 > 0.

B.2

0.8 pt𝛼 = −1𝛽=1Part C. Electrophoresis (2.7 points)
C.1
For particles with velocity 𝑣 (> 0), only those in the range 𝑥0 − 𝑣𝛿 ≤ 𝑥 ≤ 𝑥0 pass the position 𝑥0
during a time interval 𝛿. Therefore, the number of such particles per unit cross-sectional area and perunit time is given by𝑥

𝑁+ (𝑥0 ) =01
1∫𝑛(𝑥)𝑑𝑥𝛿 𝑥0 −𝑣𝛿 2(S1.17)

Using the Taylor expansion 𝑛(𝑥) ≃ 𝑛(𝑥0 ) + (𝑥 − 𝑥0 ) 𝑑𝑛𝑑𝑥 (𝑥0 ) and integrating, we obtain
𝑁+ (𝑥0 ) =

C.1

C.2

1
1 𝑑𝑛
𝑛(𝑥0 )𝑣 −(𝑥 )𝑣2 𝛿.
24 𝑑𝑥 0(S1.18)0.5 pt

1 𝑑𝑛
1(𝑥 )𝑣2 𝛿
𝑁+ (𝑥0 ) = 𝑛(𝑥0 )𝑣 −2
4 𝑑𝑥 0

Let 𝑁− (𝑥0 ) be the counterpart of 𝑁+ (𝑥0 ) for particles with velocity −𝑣, then𝑁− (𝑥0 ) =1
1 𝑑𝑛𝑛(𝑥0 )𝑣 +(𝑥 )𝑣2 𝛿.
24 𝑑𝑥 0(S1.19)With this equation, Eq. (S1.18), and 𝐽𝐷 (𝑥0 ) = ⟨𝑁+ (𝑥0 ) − 𝑁− (𝑥0 )⟩, we obtain
𝐽𝐷 (𝑥0 ) = −

1 𝑑𝑛
1 𝑑𝑛
(𝑥0 )⟨𝑣2 ⟩𝛿 = −(𝑥 )𝐶𝛿.
2 𝑑𝑥
2 𝑑𝑥 0(S1.20)Comparing this with Eq. (4) in the question sheet for 𝑥 = 𝑥0 , 𝐽𝐷 (𝑥0 ) = −𝐷 𝑑𝑛𝑑𝑥 (𝑥0 ), we obtain
𝐷=

1
𝐶𝛿.
2

(S1.21)

Plugging this into the result of B.1, we obtain(S1.22)⟨Δ𝑥(𝑡)2 ⟩ = 2𝐷𝑡.

3

Solutions to Theory Problems

S1‒4
C.2

0.7 pt

1 𝑑𝑛
𝐽𝐷 (𝑥0 ) = −(𝑥 )𝐶𝛿
2 𝑑𝑥 0
1
𝐷 = 𝐶𝛿
2⟨Δ𝑥(𝑡)2 ⟩ = 2𝐷𝑡

C.3

The force balance sketched in Fig. 2 is expressed by the following equation:(S1.23)

Π(𝑥)𝐴 + 𝑛(𝑥)𝐴Δ𝑥𝑄𝐸 = Π(𝑥 + Δ𝑥)𝐴.

Using the van 't Hoff equation for the osmotic pressure, Π(𝑥) = 𝑛(𝑥)𝑘𝑇 , and carrying out the Taylor
expansion of 𝑛(𝑥 + Δ𝑥), we obtain
𝑑𝑛
𝑛(𝑥)
=
𝑄𝐸.
𝑑𝑥
𝑘𝑇

C.3

C.4

(S1.24)0.5 pt

𝑑𝑛
𝑛(𝑥)
=
𝑄𝐸
𝑑𝑥
𝑘𝑇

The equation of motion for ⟨𝑣(𝑡)⟩ is𝑀𝑑⟨𝑣(𝑡)⟩= −𝛾⟨𝑣(𝑡)⟩ + 𝑄𝐸.
𝑑𝑡(S1.25)

By solving this with the initial condition ⟨𝑣(0)⟩ = 0, we obtain⟨𝑣(𝑡)⟩ =𝑄𝐸(1 − 𝑒−𝑡/𝜏 ).
𝛾(S1.26)

Therefore,𝑢 = lim ⟨𝑣(𝑡)⟩ =
𝑡→∞

𝑄𝐸
.
𝛾

(S1.27)▷ Note: The student is expected to surmise that the solution to Eq. (S1.25) has a functional form analogous to that to Eq. (S1.2), whose solution is given in the question sheet.

C.4

0.5 pt𝑄𝐸⟨𝑣(𝑡)⟩ =(1 − 𝑒−𝑡/𝜏 )𝛾𝑢 = 𝑄𝐸𝛾

C.5

From the result of C.3 and Eq. (4) in the question sheet, we have𝐽𝐷 (𝑥) = −

𝐷𝑄𝐸
𝑛(𝑥).
𝑘𝑇

(S1.28)4

Solutions to Theory Problems

S1‒5
From the result of C.4 and Eq. (5) in the question sheet, we have
𝐽𝑄 (𝑥) =

𝑄𝐸
𝑛(𝑥).
𝛾

(S1.29)Plugging these into the flux balance condition, 𝐽𝐷 (𝑥) + 𝐽𝑄 (𝑥) = 0, we obtain
𝐷=

C.5

𝑘𝑇
.
𝛾

(S1.30)0.5 pt𝑘𝑇
𝐷=
𝛾Part D. Mean square displacement (2.4 points)
D.1 Combining the results of C.2 and C.5, 𝑘 = 𝑅/𝑁𝐴 , 𝛾 = 6𝜋𝑎𝜂, we obtain the following equation thatlinks the mean square displacement to 𝑁𝐴 :⟨Δ𝑥2 ⟩ =𝑅𝑇 Δ𝑡.
3𝜋𝑎𝜂𝑁𝐴(S1.31)

From the data given in the question sheet, the mean square displacement is estimated at ⟨Δ𝑥2 ⟩ =6.34 𝜇m2 . Plugging this and the values of the parameters given in the question sheet, we obtain(S1.32)𝑁𝐴 = 5.6 × 1023 mol−1 .

▷ Note: In 1908, Jean Baptiste Perrin (1870-1942) carried out such an observation and obtained an estimate of 𝑁𝐴 , which turned out to be consistent with the values known at that time by other approaches.
This convinced the community of the fact that molecules and hence atoms do exist as constituents ofmatter. Perrin was awarded the Nobel Prize in Physics in 1926 for ``his work on the discontinuous structure of matter, and especially for his discovery of sedimentation equilibrium''. For more details, see, e.g.,
S. G. Brush, ``A History of Random Processes: I. Brownian Movement from Brown to Perrin'', Archive for
History of Exact Sciences, volume 5, pages 1−36 (1968).
▷ Note: On May 20, 2019, the definition of physical constants including the Avogadro constant 𝑁𝐴 waschanged. As a result, 𝑁𝐴 is now defined by a fixed value, not to be determined through measurements.

D.1

D.2

1.0 pt𝑁𝐴 = 5.6 × 1023 mol−1
𝑁

Using Δ𝑥(𝑡) = ∑𝑛=1 (𝑢 + 𝑣𝑛 )𝛿 and Eq. (3) in the question sheet, we obtain(S1.33)⟨Δ𝑥2 ⟩ = (𝑢𝑡)2 + 2𝐷𝑡
for general 𝑡. This can be rewritten as⟨Δ𝑥2 ⟩ = 𝑢2 𝑡 (𝑡 +2𝐷
) = 𝑢2 𝑡(𝑡 + 𝑡∗ ),𝑢2(S1.34)

with 𝑡∗ = 2𝐷/𝑢2 . Therefore,𝑡⟨Δ𝑥2 ⟩ ∝ { 2𝑡

for 𝑡 ≪ 𝑡∗
for 𝑡 ≫ 𝑡∗

(S1.35)5Solutions to Theory Problems

S1‒6
D.2

0.8 pt⟨Δ𝑥2 ⟩ = (𝑢𝑡)2 + 2𝐷𝑡 for general 𝑡𝑡⟨Δ𝑥2 ⟩ ∝ { 2𝑡𝑡∗ =for small 𝑡
for large 𝑡

2𝐷𝑢2

An example of the graph to answer:(log t*)D.1
Since the microbe does not change the swimming direction for 𝑡 ≪ 𝛿0 , we can use the result of
D.2 just by replacing 𝑢 by 𝑢0 . By contrast, for 𝑡 ≫ 𝛿0 , the motion of the microbe can be described by themodel considered in PART B, though its parameter 𝛿 is not an artificial parameter anymore but is now aquantity that characterizes the microbe's motion, 𝛿0 . The parameter 𝐶 is given by 𝐶 = 𝑢20 . Plugging this
into Eq. (S1.14) and collecting all these results, we obtain⎧2𝐷𝑡
for 𝑡 ≪ 2𝐷/𝑢20{⟨Δ𝑥2 ⟩ = ⎨𝑢20 𝑡2 for 2𝐷/𝑢20 ≪ 𝑡 ≪ 𝛿0
{𝑢2 𝛿 𝑡 for 𝛿 ≪ 𝑡⎩ 0 0
0(S1.36)▷ Note: More precisely, one can show ⟨Δ𝑥2 ⟩ = (𝑢20 𝛿0 + 2𝐷)𝑡 for 𝑡 ≫ 𝛿0 . However, in order for the intermediate regime to exist, we have 2𝐷/𝑢20 ≪ 𝛿0 , from which it follows that 𝑢20 𝛿0 ≫ 2𝐷 and the expressionin Eq. (S1.36) is a good approximation.
▷ Note: The motion of the microbe described here is called the run-and-tumble motion, except that
it is usually assumed that the microbe changes the swimming direction (``tumbling'') at random timeintervals. Some bacteria including Escherichia coli is known to swim in this manner.

D.3

0.6 pt⎧2𝐷𝑡
for small 𝑡{⟨Δ𝑥2 ⟩ = ⎨𝑢20 𝑡2 for intermediate 𝑡{𝑢2 𝛿 𝑡 for large 𝑡⎩ 0 0Part E. Water purification (1.5 points)
E.1 The interaction energy 𝑈 (𝑑) has a barrier if 𝑐 is small enough, but the barrier disappears if 𝑐 exceeds
a threshold. This threshold is the critical concentration to derive in this question. The condition for thebarrier to disappear is given by(S1.37)min 𝑈 ′ (𝑑) = 0.
6

Solutions to Theory Problems

S1‒7This can be expressed by the following two equations:𝐴
𝐵𝜖(𝑘𝑇 )2 −𝑑/𝜆
−
𝑒
= 0,
𝑑2
𝑞2 𝜆
2𝐴 𝐵𝜖(𝑘𝑇 )2 −𝑑/𝜆𝑈 ″ (𝑑) = − 3 +𝑒= 0.
𝑑𝑞 2 𝜆2(S1.38)𝑈 ′ (𝑑) =(S1.39)Solving these, we obtain𝑑 = 2𝜆 = √𝐴𝑞 2 𝜆𝐵𝜖(𝑘𝑇 )2

(S1.40)and therefore𝜆=𝑒2 𝐴𝑞 2.
4𝐵𝜖(𝑘𝑇 )2

Plugging this into 𝑐 =𝑐=(S1.41)𝜖𝑘𝑇 −2𝜆 , we obtain
2𝑁𝐴 𝑞 28𝐵2 𝜖3 (𝑘𝑇 )5.
𝑒4 𝑁𝐴 𝐴2 𝑞 6(S1.42)▷ Note: In the literature, it is also common to consider that the critical concentration is reached whenthe energy barrier becomes as low as the energy for 𝑑 → ∞, i.e., max 𝑈 (𝑑) = 0, although this does
not meet the requirements given in the question sheet. If this condition is used instead, we find 𝑐 =𝐵2 𝜖3 (𝑘𝑇 )5. This differs from Eq. (S1.42) only by a factor 𝑒2 /8 ≈ 0.92.
2𝑒2 𝑁 𝐴2 𝑞6
𝐴

E.1

1.5 pt8𝐵2 𝜖3 (𝑘𝑇 )5𝑐= 4
𝑒 𝑁𝐴 𝐴 2 𝑞 6

7

Solutions to Theory Problems

S2‒1
Theory Problem 2: Neutron Stars (10 points)
Part A. Mass and stability of nuclei (2.5 points)
A.1
The given binding energy is often called the Weizsäcker-Bethe mass formula, and the physicalinterpretation of the volume and the surface terms is based on the liquid drop model. The formula
works quite well except for the shell effects. Find 𝐴 to minimize the binding energy per mass number,
i.e.,
𝑎
𝐵
= 𝑎𝑉 − 𝑎𝑆 𝐴−1/3 − 𝐶 𝐴2/3 .
𝐴
4(S2.1)

As long as 𝐴 is small, the second term is dominantly increasing with increasing 𝐴, and it is eventuallytaken over by the third term which is decreasing. Therefore, the extremal corresponds to the maximumof 𝐵/𝐴. One can explicitly carry out𝑑(𝐵/𝐴)=0𝑑𝐴(S2.2)

to find the following condition,𝑎𝑆 −4/3 𝑎𝐶 −1/3
𝐴
−
𝐴
= 0.
3
6

(S2.3)The solution is
𝐴=

2𝑎𝑆
.
𝑎𝐶

(S2.4)

From the given numerical values, 𝐴 = 50 (which must be an integer) is concluded.
▷ Note: In reality 𝐵/𝐴 has a maximum for 𝐴 ranging from 56 Fe to 62 Ni. The discrepancy from the answer
in this problem is understood by the approximation of dropping the pairing energy and disregarding a
mass difference between the proton and the neutron.

A.1

0.9 pt𝐴 = 50

A.2

Take the differentiation of 𝐵(𝑍, 𝐴 − 𝑍)/𝐴 with respect to 𝑍 for a fixed 𝐴, which leads to−2𝑎𝐶

𝑍∗
2𝑍 ∗ − 𝐴− 4𝑎sym
= 0.
1/3
𝐴
𝐴

(S2.5)

By solving this in terms of 𝑍 ∗ , one finds
𝑍∗ =

1
𝐴
⋅ .
𝑎𝐶
1+
𝐴2/3 24𝑎sym(S2.6)

From this expression one can understand that 𝑍 ∗ ≃ 𝑁 as long as 𝐴 is small enough, while 𝑍 ∗ becomes far
smaller than 𝑁 for large 𝐴. It is obvious from the explicit form that the symmetry energy tends to favor
𝑍 = 𝑁 but the Coulomb interaction tends to favor 𝑍 → 0, and the balance between these competing
effects determines 𝑍 ∗ . Nuclei with too many neutrons (protons) would go through the 𝛽 − decay (the 𝛽 +decay or the electron capture) toward the stable (𝑍, 𝑁 ).
A.2

0.9 pt𝑍 ∗ = 791

Solutions to Theory Problems

S2‒2
A.3 Plugging the binding energy into the given inequality, one sees that the volume terms cancel due
to volume conservation. Then, the condition involves only 𝑎𝑆 and 𝑎𝐶 which are related as
2/3

𝑎𝑆 [𝐴

𝐴
− 2( )
2

2/3] + 𝑎𝐶 [(𝑍/2)2𝑍2−
2] > 0.
𝐴1/3(𝐴/2)1/3(S2.7)

As guided in the problem, the above inequality becomes as simple as21/3 − 1 𝑎𝑆
𝑍2
>
⋅
.
𝐴
1 − 2−2/3 𝑎𝐶(S2.8)

Therefore, the numerical coefficient turns out to be 0.7.
▷ Note: The physical interpretation of this result may need some explanations. Using the values of𝑎𝑆 and 𝑎𝐶 , one finds that such a symmetric fission process is possible for 𝑍 2 /𝐴 ≳ 18. For example,
lead (Pb) with 𝑍 = 82 and 𝐴 = 208 is a stable element among several isotopes. Now, one can compute822 /208 ≈ 32, which is larger than the threshold 18. The key to resolving this gap is the potential barrier
from the deformation. When a heavy nucleus splits into two fragments, the shape and the surface shouldchange from the stable configuration (which is not necessarily spherical due to interaction) and thus
the surface energy increases. Although some heavy elements are energetically unstable, the lifetime
necessary to overcome the potential barrier can be very large.

A.3

0.7 pt𝐶fission = 7.0 × 10−1

Part B. Neutron star as a gigantic nucleus (1.5 points)
B.1

The expression apart from the parametric dependence on 𝐴 can be identified as𝑎grav =

3 𝐺𝑚2𝑁,
5 𝑅0(S2.9)

which is re-expressed in terms of 𝑀𝑃 using the given relation to 𝐺, leading to𝑎grav =

3 ℏ𝑐 𝑚2𝑁
3 197 fm ⋅ MeV × (939 MeV/𝑐2 )2≃ 6.4 × 10−37 MeV .
=⋅5 𝑅0 𝑀𝑃2
5 1.1 fm × (1.22 × 1022 MeV/𝑐2 )2(S2.10)Here, 𝑀𝑃 is a quantity often called the Planck mass. The gravitational effect is extremely tiny as comparedto the typical scale in nuclear physics and this scale difference is manifest for this expression of 𝐺 with
𝑀𝑃 in the MeV unit.
The stability is judged from the condition that the binding energy should be positive, i.e.,(S2.11)

𝐵total (𝐴) = 𝑎𝑉 𝐴 − 𝑎sym 𝐴 + 𝑎grav 𝐴5/3 > 0 .
This inequality can be translated into 𝐴 > 𝐴𝑐 with 𝐴𝑐 given by
𝐴𝑐 = (

𝑎sym − 𝑎𝑉 3/2) ≃ 4.4 × 1055 .
𝑎grav(S2.12)▷ Note: One may think that one neutron drip is a process with the least change in the surface area
and thus the smallest barrier. This leads to a condition, 𝐵total (𝐴) > 𝐵total (𝐴 − 1) or approximately
𝑑𝐵total (𝐴)/𝑑𝐴 > 0, which is satisfied in a window with 𝐵total < 0. This condition, 𝑑𝐵total /𝑑𝐴 = 0, results insmaller 𝐴𝑐 but it is nontrivial whether such an unstable initial state could be prepared in the nature. The
neutron star is born in the Type-II (core-collapse) supernovae, and a baby star called the proto-neutronstar is an energetic state at high temperature. Neutrinos bring heat out from the proto-neutron star2

Solutions to Theory Problems

S2‒3
within the time scale of 𝒪(10) seconds. What is the possible smallest mass of the neutron star? This
is not completely understood partly because the computer simulation of the supernovae is a big challenge even today. Although the neutron star mass can become much smaller than 𝑀⊙ theoretically, thesimulation and the observation favor the mass ≳ 1.4𝑀⊙ .

B.1

1.5 pt𝑎grav = 6 × 10−37 MeV
𝐴𝑐 = 4 × 1055

Part C. Neutron star in a binary system (6.0 points)
C.1
From the energy conservation, the free-falling system earns the kinetic energy 12 𝑚𝑣2 from thepotential energy 𝑚𝑔Δℎ, and the velocity takes(S2.13)𝑣2 = 2𝑔Δℎ = 2Δ𝜙 .

The time delay can be derived from the standard arguments. Suppose that Clock-II passes two infinitesimally separate points, 𝑧 and 𝑧 + Δ𝑧, in F at time 𝑡 and 𝑡 + Δ𝜏II , then the time interval registered by Clock-II
isΔ𝜏II =𝛾(𝑐Δ𝜏F − 𝛽Δ𝑧) ,𝑐(S2.14)

where the Lorentz transformation is used1 with 𝛽 = 𝑣/𝑐 and 𝛾 = 1/√1 − 𝛽 2 . Because Δ𝑧/Δ𝜏F = 𝑣 andΔ𝜏F = Δ𝜏I , the above expression is written as(S2.15)Δ𝜏II = 𝛾(1 − 𝛽 2 )Δ𝜏F = √1 − 𝛽 2 Δ𝜏I .
Using the expression of 𝑣2 , one finally arrives at
Δ𝜏II = √1 − 2Δ𝜙Δ𝜙Δ𝜏I ≃ (1 − 2 ) Δ𝜏I .
𝑐2
𝑐(S2.16)C.1

1.0 ptΔ𝜙Δ𝜏II = (1 − 2 )Δ𝜏I
𝑐

C.2 In terms of the effective speed of light, the total time necessary for the light propagation from N
to E is𝑥𝐸

𝑡E-N = ∫𝑥𝑁𝑑𝑥.
𝑐eff (𝑥)(S2.17)The denominator is expanded in terms of the gravitational potential and the leading-order correction isfound to be𝑥𝑡E-N ≃𝐸
2𝐺𝑀
𝑥 − 𝑥𝑁1∫ 𝑑𝑥(1 + √ WD ) = 𝐸+ Δ𝑡 ,
22
2𝑐 𝑥𝑁
𝑐𝑐 𝑥 +𝑑

(S2.18)

1 Clock-F is in an inertial frame but Clock-II is not. Using Clock-II′ in another free-falling frame II′ as an inertial reference toClock-II, the Lorentz transformation is validated for Clock-II′ seen from Clock-F.

3

Solutions to Theory Problems

S2‒4
where the time delay Δ𝑡 is identified as
√
𝑥=𝑥𝐸
𝑥𝐸
2𝐺𝑀WD
𝑑𝑥
𝐺𝑀WD
𝑥2 + 𝑑2 + 𝑥
√
√
∫
)∣
=
.
Δ𝑡 =
log(
𝑐3
𝑐3
𝑥2 + 𝑑2
𝑥2 + 𝑑2 − 𝑥 𝑥=𝑥𝑥𝑁(S2.19)𝑁

Inside the logarithm, the following approximations are made:√𝑥2𝑁 + 𝑑2 + 𝑥𝑁 ≃𝑑2,
2|𝑥𝑁 |√𝑥2𝐸 + 𝑑2 − 𝑥𝐸 ≃

𝑑2
,
2𝑥𝐸

√𝑥2𝑁 + 𝑑2 − 𝑥𝑁 ≃ 2|𝑥𝑁 | ,(S2.20)and√𝑥2𝐸 + 𝑑2 + 𝑥𝐸 ≃ 2𝑥𝐸 .

(S2.21)

Then, the simple form of approximated Δ𝑡 is
Δ𝑡 ≃

𝐺𝑀WD
2𝑥𝐸 ⋅ 2|𝑥𝑁 |2𝐺𝑀WD
4|𝑥 |𝑥)=log( 2log( 𝑁2 𝐸 ) .
𝑐3
𝑑 /(2𝑥𝐸 ) ⋅ 𝑑2 /(2|𝑥𝑁 |)
𝑐3
𝑑

C.2

(S2.22)

1.8 pt4|𝑥 |𝑥2𝐺𝑀WDlog( 𝑁2 𝐸 )
Δ𝑡 =
3
𝑐
𝑑

C.3

Because |𝑥𝑁 | = 𝐿 cos 𝜀 ≃ 𝐿 and 𝑑 = 𝐿 sin 𝜀 ≃ 𝐿𝜀 for Δ𝑡max , the answer of C.2 gives
Δ𝑡max =

2𝐺𝑀WD
log(4𝑥𝐸 /𝐿𝜀2 )𝑐3(S2.23)

For Δ𝑡min the sign of 𝑥𝑁 is changed. Although the expression of Δ𝑡 is intact, the approximation takes adifferent form as√𝑥2𝑁 + 𝑑2 + 𝑥𝑁 ≃ 2𝑥𝑁 ,√𝑥2𝑁 + 𝑑2 − 𝑥𝑁 ≃

𝑑2
.
2𝑥𝑁

(S2.24)

Then, the approximated form of Δ𝑡min is
Δ𝑡min ≃

𝐺𝑀WD
2𝑥 ⋅ 𝑑2 /(2𝑥𝑁 )2𝐺𝑀WD
log( 2 𝐸)=log(𝑥𝐸 /𝐿) ,3𝑐𝑑 /(2𝑥𝐸 ) ⋅ 2𝑥𝑁
𝑐3(S2.25)where 𝑥𝑁 ≃ 𝐿 is used in the last expression. In the difference, Δ𝑡max − Δ𝑡min , one sees that 𝐿 and 𝑥𝐸
disappear.
C.3

C.4

1.8 pt

2𝐺𝑀WD
Δ𝑡max − Δ𝑡min =log(4/𝜀2 )𝑐3Using the expansion, cos 𝜀 ≃ 1 − 12 𝜀2 , one can evaluate(S2.26)𝜀2 ≃ 2 × (1 − cos 𝜀) = 0.00022 .
From the graph the difference in time delays is roughly read out as(S2.27)

Δ𝑡max − Δ𝑡min ≈ 50 𝜇s
From these numerical values, 𝑀WD is solved as−1

𝑀WD = 𝑀⊙ (

2𝐺𝑀⊙
)
𝑐3

Δ𝑡max − Δ𝑡min
50 𝜇s≃
𝑀 ≃ 0.5 𝑀⊙ .
log(4/𝜀2 )10 𝜇s log(4/0.00022) ⊙4(S2.28)

Solutions to Theory Problems

S2‒5▷ Note: The data in this problem roughly correspond to PSR J1614-2230 [see P.B. Demorest et al., Nature
467, 1080-1083 (2010)]. From the Shapiro delay measurement, the White Dwarf mass was estimated as0.500 ± 0.006𝑀⊙ . With the Keplerian orbital parameters in the binary system, the neutron star mass wasconsidered to be 1.97 ± 0.04𝑀⊙ , which was the heaviest neutron star at that time. Since then, several
candidates for heavier neutron stars have been found.

C.4

0.8 pt
𝑀WD /𝑀⊙ = 0.5

C.5

For the circular orbit with the radius 𝑅, the equation of motion is𝑚𝑅𝜔2 = 𝐺𝑚𝑀,
𝑅2(S2.29)if 𝑀 is sufficiently large. From this it is easy to see(S2.30)𝑅3 𝜔2 = 𝐺𝑀 = (const.)

This is nothing but Kepler's third law and the relation holds for more general elliptical orbits around thecenter of mass.
C.5

C.6

0.4 pt3
𝑝=−2
The sum of the kinetic energy and the potential energy is
𝐸=

1𝑚𝑀
𝑚𝑅2 𝜔2 − 𝐺.
2𝑅(S2.31)

From the equation of motion this is rewritten as
1 𝑚𝑀
𝐸=− 𝐺
.
2
𝑅

(S2.32)

Therefore, when 𝐸 decreases due to gravitational wave emission, 𝑅 should decrease. Then, 𝜔 should
increase. Since the amplitude is proportional to 𝑅2 𝜔2 ∝ 𝑅−1 , it should increase. In summary, both thefrequency and the amplitude should increase as time goes on, as illustrated in (b).
C.6

0.2 pt

The most appropriate profile is (b).

5

Q3-1

TheoryEnglish (Official)

Water and Objects (10 pt)
In this problem, we consider the phenomena caused by the interaction between water and objects, related to surface tension. Part A treats motion, while Parts B and C are regarding static situations.
If necessary, you can use the fact that if the function 𝑦(𝑥) satisfies
the differential
equation 𝑦″ (𝑥) = 𝑎𝑦(𝑥)√√(𝑎 is a positive constant), then its general solution is 𝑦(𝑥) = 𝐴𝑒 𝑎𝑥 + 𝐵𝑒− 𝑎𝑥 , where 𝐴 and 𝐵 are arbitrary
constants.

Part A. Merger of water drops (2.0 points)
As shown in Fig.1, we consider two stationary, spherical water drops on the surface of a superhydrophobic material, i.e., very strong repulsive force exists between material and water.
Initially neighboring two identical spherical water drops are placed on the surface; then these two drops
are merged after touching each other and form a larger spherical water drop, which suddenly jumps up.
A.1

The radius 𝑎 of both water drops before the merger is 100 𝜇m. The density ofwater 𝜌 is 1.00 × 103 kg/m3 . The surface tension 𝛾 is 7.27 × 10−2 J/m2 .
A portion 𝑘 of the difference of the surface energy before and after the merger,
ΔE, is transformed into the kinetic energy of the jumped water drop. Then, determine the initial jump-up velocity, 𝑣, of the merged water drop in two significant digits under the following assumptions:• 𝑘 = 0.06
• Before and after merger, the total volume of water is conserved.

2.0pt

Fig. 1: Merger of two water drops and jump of the merged water drop.

Part B. A vertically placed board (4.5 points)
A flat board is immersed vertically in water. Figures 2(a) and 2(b) respectively show water surface forms
for the hydrophilic (attractive) and hydrophobic board materials. We neglect the thickness of the board.
The board surface is on the 𝑦𝑧 plane, and the horizontal water surface far away from the board is on
the 𝑥𝑦 plane with 𝑧 = 0. The surface shape does not depend on the 𝑦-coordinate. Let 𝜃(𝑥) be the angle
between the water surface and the horizontal plane at a point (𝑥, 𝑧) on the water surface in the 𝑥𝑧 plane.
Here 𝜃(𝑥) is measured with respect to the positive 𝑥 axis and the counterclockwise rotation is taken as
positive. Let 𝜃(𝑥) be 𝜃0 at the point of contact between the board and the water surface (𝑥 = 0). In thefollowing, 𝜃0 is fixed by the properties of the board material.
Water density 𝜌 is constant and water surface tension 𝛾 is uniform. The gravitational acceleration constant is given by 𝑔. The atmospheric pressure, 𝑃0 , is assumed to be always uniform. Let us determine
the water surface form in the following steps. Note that the unit of surface tension is J/m2 as well as N/m.

Theory

Q3-2
English (Official)

Fig. 2: Boards vertically immersed in the water. (a) hydrophilic board case;(b) hydrophobic board case.
B.1

We consider a hydrophilic board case, as shown in Fig.2(a). We note that thewater pressure, 𝑃 , satisfies the conditions 𝑃 < 𝑃0 for 𝑧 > 0 and 𝑃 = 𝑃0 for𝑧 = 0. Then, express 𝑃 at 𝑧 in terms of 𝜌, 𝑔, 𝑧, and 𝑃0 .

0.6pt

B.2

We consider a water block whose cutout is shown as shaded in Fig.3(a). Its 𝑥𝑧
plane cross-section is shown in a hatched area in Fig.3(b). Let 𝑧1 and 𝑧2 respectively be the left and right edge coordinates of the boundary (water surface)
between the water block and the air.
Obtain a horizontal component (𝑥 component) of the net force per unit length
along the 𝑦-axis, 𝑓𝑥 , which is exerted on the water block due to the pressure, interms of 𝜌, 𝑔, 𝑧1 , and 𝑧2 . Note that 𝑃0 results in no net horizontal force on thewater block.

0.8pt

Q3-3

TheoryEnglish (Official)

Fig. 3: Cutout form of water block on the water surface. (a) Bird's eye view and (b) crosssectional view.
B.3

Surface tension acting on the water block is balanced with the force 𝑓𝑥 discussed
in B.2. We respectively define 𝜃1 and 𝜃2 as the angles between the water surface
and the horizontal plane at the left and right edges. Express 𝑓𝑥 in terms of 𝛾,𝜃1 , and 𝜃2 .

0.8pt

B.4

The following equation holds at an arbitrary point (𝑥, 𝑧) on the water surface,

0.8pt

1 𝑧 𝑎
( ) + cos 𝜃(𝑥) = constant.
(1)
2 ℓ
Determine the exponent 𝑎 and express the constant ℓ in terms of 𝛾 and 𝜌. Notethat this equation holds regardless of hydrophilic or hydrophobic board materials.
B.5

In Eq. (1) in B.4, we assume that variation of the water surface is slow, i.e.,|𝑧′ (𝑥)| ≪ 1, so that we can expand cos 𝜃(𝑥) with respect to 𝑧 ′ (𝑥) up to the second
order. Then, differentiating the resultant equation with respect to 𝑥, we obtain
the differential equation satisfied by 𝑧(𝑥). Solve this differential equation anddetermine 𝑧(𝑥) for 𝑥 ≥ 0 in terms of tan 𝜃0 and ℓ. Note that the vertical directionsof Figs. 2 and 3 are exaggerated for better view and they do not satisfy thecondition, |𝑧 ′ (𝑥)| ≪ 1.

1.5pt

Part C. Interaction between two rods (3.5 points)
The identical rods A and B made of the same material floating in parallel on the water surface are placedat the same distance away from the 𝑦-axis (Fig.4).

Theory

Q3-4
English (Official)

Fig. 4: Two rods A and B floating on the water surface.
C.1

At the contact points of the rod B and the water surface, we define the 𝑧coordinates 𝑧a and 𝑧b , and the angles 𝜃a and 𝜃b , as shown in Fig.5. Determine
the horizontal force component, 𝐹𝑥 , on the rod B per unit length along the 𝑦-axis
in terms of 𝜃a , 𝜃b , 𝑧a , 𝑧b , 𝜌, 𝑔, and 𝛾.

1.0pt

Fig. 5: Vertical cross-sectional view of two rods floating on the water surface.
C.2

We define the 𝑧-coordinate of the water surface, 𝑧0 , at the midpoint of two rodsin the 𝑥𝑧 plane. Express the force 𝐹𝑥 obtained in C.1 without using 𝜃a , 𝜃b , 𝑧a , and
𝑧b .

1.5pt

C.3

Let 𝑥a be the 𝑥-coordinate of the contact point between the water surface andthe left side of the rod B. Using the differential equation obtained in B.5, express
the water level coordinate 𝑧0 of the midpoint of these two rods A and B in termsof 𝑥a and 𝑧a . You can use the constant ℓ introduced in B.4.

1.0pt

Solutions to Theory Problems

S3‒1
Theory Problem 3: Water and Objects (10 points)
Part A. Merger of water drops (2.0 pt)
A.1

The surface energy per drop before the merger is(S3.1)

𝐸 = 4𝜋𝑎2 𝛾.
Therefore, the surface energy difference becomes(S3.2)

Δ𝐸 = 4𝜋 (2 − 22/3 ) 𝑎2 𝛾.
The transfer of surface energy to kinetic energy is represented by(S3.3)

𝑀 𝑣2 /2 = 𝑘Δ𝐸,

where 𝑘 = 0.06 and 𝑀 = 4𝜋𝑎3 𝜌/3 × 2 = 8𝜋𝑎3 𝜌/3 is the mass of the drop after the merger. The numericalcomputation gives
𝑣=√

2𝑘Δ𝐸
𝑘𝛾
0.06 × (7.27 × 10−2 )= √3 (2 − 22/3 )= √3 (2 − 22/3 ) ×= 0.232 m/s.
𝑀𝜌𝑎(1.0 × 103 ) × (100 × 10−6 )(S3.4)▷ Note: We point out an interesting phenomenon related to this question. On a superhydrophobic surface, when small droplets merge, they release surface energy, causing the surface area to shrink. This
energy release propels the merged droplet to jump up. This phenomenon mirrors the natural mechanism seen in cicadas. Cicadas' wings, which possess superhydrophobic surfaces, facilitate the removal
of water droplets upon coalescence. This process serves as a natural self-cleaning system, converting
surface energy to kinetic energy, as reported in the following paper: Wisdom et. al., Proc. Natl. Acad. Sci.
USA 110, 7992−7997 (2013).

A.1

2.0 pt𝑣 = 0.23 m/s

Part B. A vertically placed board (4.5 pt)
B.1
Consider a vertical upright column-shaped water block as shown in thehatched area of Fig. S3-1. The vertical force balance with respect to thisblock per unit area leads to 𝑃 + 𝜌𝑔𝑧 = 𝑃0 .

Fig. S3-1
B.1

0.6 pt𝑃 = 𝑃0 − 𝜌𝑔𝑧

B.2
Because the atmospheric pressure 𝑃0 exerts no net horizontal force on the water block, we have𝑧1

𝑓𝑥 = ∫ (−𝜌𝑔𝑧)𝑑𝑧 =𝑧2

1𝜌𝑔 (𝑧22 − 𝑧12 ) .
2(S3.5)

This force acts in the leftward direction.
1

Solutions to Theory Problems

S3‒2▷ Note: The reason why 𝑃0 exerts no net horizontal force is understood as follows. Consider a small
area (infinitesimally divided piece) near the surface, which is regarded as a right-angled triangle (seeFig. S3-2).

Fig. S3-2
The horizontal component of the combined force exerted on the right-angled triangle ABC per unit
length along the 𝑦-axis by atmospheric pressure is
𝑃0 × AB − 𝑃0 × AC ×

AB
=0
AC

Integrating infinitesimal pieces over a finite domain yields a finite volume of water, while the net force
remains zero.

B.2

0.8 pt1
𝑓𝑥 = 𝜌𝑔 (𝑧22 − 𝑧12 )2

B.3
The horizontal component of the surface tension acting on the water block is 𝛾 cos 𝜃2 − 𝛾 cos 𝜃1 . Thus,
the horizontal force balance is expressed as(S3.6)

𝑓𝑥 + 𝛾 cos 𝜃2 − 𝛾 cos 𝜃1 = 0.

B.3

0.8 pt𝑓𝑥 = 𝛾 cos 𝜃1 − 𝛾 cos 𝜃2

B.4
From the results of B.2 and B.3, we have11𝜌𝑔𝑧12 + 𝛾 cos 𝜃1 = 𝜌𝑔𝑧22 + 𝛾 cos 𝜃2 .
2
2

(S3.7)

Since this equation holds at an arbitrary point (𝑥, 𝑧) on the water surface, we conclude1
𝜌𝑔𝑧 2 + 𝛾 cos 𝜃 = constant,
2(S3.8)

which is written as
1 𝑧 𝑎( ) + cos 𝜃(𝑥) = constant,
2 ℓwith 𝑎 = 2 and ℓ = √(S3.9)𝛾.
𝜌𝑔▷ Note: The equaiton (S3.9) is a kind of conservation law. The constant ℓ is called the capillary length.

2

Solutions to Theory Problems

S3‒3
B.4

0.8 pt𝛾𝑎 = 2, ℓ = √𝜌𝑔

B.5
The derivative of the water surface coordinate 𝑧, denoted by 𝑧 ′ , is associated with the angle ofinclination 𝜃, given by the equation: 𝑧′ = tan 𝜃. This relation yields
cos 𝜃 =

1,
√1 + (𝑧 ′ )2

(S3.10)which leads to1
cos 𝜃 ≃ 1 − (𝑧 ′ )2 .
2

(S3.11)

Plugging this into Eq. (S3.9), we obtain𝑧2− 𝑧 ′2 = const.
ℓ2(S3.12)

Taking the derivative of both sides with respect to 𝑥, we have
𝑧″ =

𝑧
,
ℓ2

(S3.13)

which is the differential equation that determines the water surface form.
Its general solution is(S3.14)𝑧 = 𝐴𝑒𝑥/ℓ + 𝐵𝑒−𝑥/ℓ .
The boundary condition, 𝑧(∞) = 0, leads to 𝐴 = 0.
The boundary condition, 𝑧′ (0) = tan 𝜃0 , leads to 𝐵 = −ℓ tan 𝜃0 .
B.5

1.5 pt𝑧 (𝑥) = −ℓ tan 𝜃0 𝑒−𝑥/ℓPart C. Interaction between two rods (3.5 pt)
C.1

The horizontal component of the force due to the pressure is𝑧b∫ (𝜌𝑔𝑧) 𝑑𝑧 =𝑧a1𝜌𝑔 (𝑧b2 − 𝑧a2 )2(S3.15)Let 𝑧bottom be the 𝑧-coordinate at the bottom of the rod. Then, we have𝑧bottom

𝑧b

𝑧b

𝑧a

𝐹𝑥 = ∫(−𝜌𝑔𝑧)𝑑𝑧 + (− ∫𝑧bottom(−𝜌𝑔𝑧)𝑑𝑧) = ∫ (𝜌𝑔𝑧)𝑑𝑧(S3.16)𝑧a▷ Note: The fact that the contribution due to the pressure does not depend on the shape of the crosssection can be demonstrated as follows. The pressure at the point 𝑠 on the contour 𝐶 along the crosssectional boundary is(S3.17)−𝑃 𝑛𝑑𝑠̂ = (−𝑃0 +𝜌𝑔𝑧)𝑛𝑑𝑠.
̂

3

Solutions to Theory Problems

S3‒4
Let 𝑥̂ be the unit vector pointing the positive 𝑥-direction and noting 𝑥̂ ⋅ 𝑛𝑑𝑠
̂ = 𝑑𝑧 (see Fig. S3-3), we obtainits horizontal component as(S3.18)−𝑃 𝑛̂ ⋅ 𝑥𝑑𝑠
̂ = −𝑃0 𝑑𝑧+𝜌𝑔𝑧𝑑𝑧.
Integrating along the contour 𝐶.1 We obtain𝑧b∫ (𝜌𝑔𝑧)𝑑𝑧 =𝑧a1𝜌𝑔 (𝑧b2 − 𝑧a2 )2(S3.19)Fig. S3-3
C.1

C.2

1.0 pt1
𝐹𝑥 = 𝜌𝑔 (𝑧b2 − 𝑧a2 ) + 𝛾 (cos 𝜃b − cos 𝜃a )2
By applying the boundary conditions to Eq. (S3.8), we obtain1
1
𝜌𝑔𝑧a2 + 𝛾 cos 𝜃a = 𝜌𝑔𝑧02 + 𝛾
⏟
2
2⏟⏟⏟⏟
⏟⏟⏟⏟⏟⏟⏟
𝑥=𝑥a(S3.20)𝑥=01
𝜌𝑔𝑧b2 + 𝛾 cos 𝜃b = 𝛾⏟2⏟⏟⏟⏟⏟⏟⏟
𝑥→∞(S3.21)𝑥=𝑥b

1Then, 𝐹𝑥 = − 𝜌𝑔𝑧02 is obtained by subtracting (S3.20) from (S3.21).
2▷ Note: The physical background of this problem is as follows. When a single rod is placed on the water
surface, the shape of the water surface on both sides of the rod remains the same. In other words, therod is placed in an environment that exhibits the left-right symmetry. Then, there is no force acting on
the rod. On the other hand, when two rods are placed on the water surface, the left-right symmetry of
the water surface is broken from the perspective of each rod. As a result, an attractive force is generated.
The displacement of the water surface at the midpoint between the two rods differs from that of a horizontal water surface. This deviation is represented by 𝑧0 . That is to say, 𝑧0 plays the role of a symmetrybreaking parameter (see Fig. S3-4).
The fact that the attractive force between the two rods is determined solely by this parameter suggeststhat the symmetry breaking directly becomes the origin of the force. This corresponds to the fundamental principle in physics that relates symmetry breaking to force generation.
1 This integral is symbolically written as ∮ (−𝑃 𝑛̂ ⋅ 𝑥𝑑𝑠).
̂𝐶

4

Solutions to Theory Problems

S3‒5

Fig. S3-4
C.2

C.3

1.5 pt1
𝐹𝑥 = − 𝜌𝑔𝑧02
2
The general solution for the water surface height is given by the equation(S3.22)𝑧(𝑥) = 𝐴𝑒𝑥/ℓ + 𝐵𝑒−𝑥/ℓ .
By considering the left-right symmetry, we find(S3.23)𝐴 = 𝐵.
Applying the boundary condition 𝑧(0) = 𝑧0 , we obtain(S3.24)

𝐴 + 𝐵 = 𝑧0 .
We thus have(S3.25)𝐴 = 𝑧0 /2, 𝐵 = 𝑧0 /2.

C.3

1.0 pt2𝑧𝑧0 = 𝑥 /ℓ a −𝑥 /ℓ𝑒 a +𝑒 a5Appendix 2
Brochures ofCultural EventsAnd
ExcursionsAppendix 3
Newsletters
No.1 - 10Monday, July 10th

one,Indonesia: NAJA Muh. Zaidan

Norway: HE Zejia

The opening ceremony was cool. It was interesting

I enjoyed the opening ceremony very much,to learn about Japanese culture. I didn't know

especially the traditional performance I have nevermuch before, but now I know about drum

seen before. I also liked the occasion that a lot of

performance and karate. It was really cool. I liked it.

contestants went up to the stage and had a chance

I like Japanese culture, such as Pokemon, anime,

to get to know each other. Since it is so hot outside

drumming, and karate. I think it is a cool culture.

today, we are not going out, but in the next few

Today, I'm going to the Pokemon Center, and I'mdays, we deﬁnitely will. I don't know much about

excited. I'm nervous about taking the exam

Japanese culture and hope to learn more this week.

tomorrow, but I have already prepared for a longtime.

Suriname: PURPERHART Nyuk-Shi
The opening ceremony was really fun. It was reallyenergetic and nice. I really liked the drum

Qatar: AL-NAJJAR Khalid

performance, which was very very passionate. It

The opening ceremony performance was great. I

looked fun when they were really hitting the drum.

liked the second drum performance the mostI had never seen that. The karate was also reallybecause it was the most fun and energetic. It has

good. It was really nice how you could see howboth music and dance aspects. It is very humid,

strong the movements were. They made a lot of

but Qatar is also as humid as Japan all year.

intimidating noises. Though I'm a little nervous
about taking the exam tomorrow, I will try my best.

Belgium: BARANI Kristina
The opening ceremony was very punctual. The
speeches were very well written. The drum andkarate performances were also very well executed.
I really like the second drum dance. I did not knowmuch about the drum, but the sound was very
loud and coordinated. About tomorrow'scompetition, I hope the line for the breakfast will
not be too long, so I will get to the test room ontime. Also, I hope the experiment problems are
not too challenging. We cross our ﬁngers thateverything will go well.

Serbia: TODOROVIĆ Sava
The opening ceremony was very well-organized,
and actually it was the best-organized ceremonythat I have ever been to. I really liked theperformances, especially the acoustic drums. I
think it shows the real Japanese culture. It was so
nice. I feel excited to take the experiment exam
tomorrow and I am wondering how well I will
perform. I am so excited to see Tokyo. For me, it is
the main part of this competition.

27℃
36℃

27℃
36℃

Students

Leaders&Observers

3Wednesday, July 12th

27℃
36℃

Thursday, July 13th

Students
7:15-8:00

Breakfast

9:00-14:00

Half-day Tokyo

Students
NYC

Excursion
16:00-19:00

Cultural/Scientiﬁc

NYC

Experience Events
18:00-19:00

Dinner

27℃
36℃

NYC

Leaders&Observers

7:15-8:00

Breakfast

8:30

Meet at the Exam Room NYC

9:00-14:00

Exam (Theory)

NYC

NYC

14:30-15:30 Lunch (light meal)

NYC

16:00-19:00 Cultural/Scientiﬁc

NYC

Experience Events
18:00-19:00 Dinner

NYC

Leaders&Observers

7:00-8:00

BreakfastNSH

7:00-8:00

Breakfast

9:00-12:30

Board meetingNSH

9:00-15:00

Half-day Tokyo

12:30-14:00

Lunch

NSH

14:00-18:00

Board Meeting

NSH

18:00-19:30

Dinner

NSH

19:30-23:00

Board Meeting

NSH

NSH

Excursion
18:00-19:30 Dinner

NSH1

Issue 1

Sunday, July 9thJapanese culture has many unique aspects, such as characters, beliefs, and values. Among various Japanesecultures, the game is popular among the young generation. In the 1970s, against the backdrop of rapid
economic growth, electronic technologies such as computers and electronic music were fostered. These
technologies are still the foundation of today's game and anime culture, such as Pokémon and NARUTO.
Let us introduce some equipment inJapanese game arcades where you canexperience this kind of culture. First of all,the game shown below is called Taiko no
Tatsujin. In this game, you beat the taiko
drum with a bachi to the rhythm.

The author is currently addicted to a
washing machine-type game called
Maimai (see photo below), in which you
tap buttons to the rhythm. These games
belong to a genre called "sound games,"
and when you are in a game center, youoften encounter people withtremendous skills who can process

UFO Catcher is a game to get cute
Pokémon goods by arm in the box
shown below, but it is easier to losemoney than in other games. The author
spent 1,800 yen to get Mimikyu, aPokémon character, with the help of agame center staﬀ.

information in a way that ordinary
people cannot follow with their eyes.

The game below is Mario Kart, a racing
game featuring characters from Super
Mario Bros.

Gacha machines shown below can also be used
to obtain mascot characters and other items.

All in all, game arcades are attractive facilities where you can enjoy
relatively healthy and unrealistic experiences for as little as 100 yen, but be
careful not to get into them too much or spend too much money.

Issue 5

5

Thursday, July 13th

Issue 1

1

Sunday, July 9th6Issue 8

5Sunday, July 16thIPhO2023 Medal Winners

Issue 10

6

Tuseday July, 18th