rajpurkar/squad huggingface dataset:
Title: Planck_constant

The "photoelectrons" emitted as a result of the photoelectric effect have a certain kinetic energy, which can be measured. This kinetic energy (for each photoelectron) is independent of the intensity of the light, but depends linearly on the frequency; and if the frequency is too low (corresponding to a photon energy that is less than the work function of the material), no photoelectrons are emitted at all, unless a plurality of photons, whose energetic sum is greater than the energy of the photoelectrons, acts virtually simultaneously (multiphoton effect)  Assuming the frequency is high enough to cause the photoelectric effect, a rise in intensity of the light source causes more photoelectrons to be emitted with the same kinetic energy, rather than the same number of photoelectrons to be emitted with higher kinetic energy.

Question: What is emitted as a result of the photoelectric effect?
Answer: photoelectrons

Question: What does the kinetic energy of a photoelectron depend on?
Answer: the frequency

Question: What happens if the photoelectron's frequency is too low?
Answer: no photoelectrons are emitted at all

Question: What is the term used when photoelectrons act virtually at the same time?
Answer: multiphoton effect

Question: What type of energy due photoelectrons emitted due to the photoelectric effect have?
Answer: kinetic

Question: What factor of the initial light source does the energy of the photoelectrons depend on?
Answer: frequency

Question: When the photon energy is less than the work function of the material the light is shone upon, how many photoelectrons are emitted?
Answer: no photoelectrons are emitted at all

Question: If the photoelectric effect is occuring, increasing the intensity of the light source causes what?
Answer: more photoelectrons to be emitted with the same kinetic energy
Title: Planck_constant

Niels Bohr introduced the first quantized model of the atom in 1913, in an attempt to overcome a major shortcoming of Rutherford's classical model. In classical electrodynamics, a charge moving in a circle should radiate electromagnetic radiation. If that charge were to be an electron orbiting a nucleus, the radiation would cause it to lose energy and spiral down into the nucleus. Bohr solved this paradox with explicit reference to Planck's work: an electron in a Bohr atom could only have certain defined energies En

Question: Who introduced the first quantized model of the atom?
Answer: Niels Bohr

Question: When was the first quantized model of the atom introduced?
Answer: 1913

Question: Why was the first quantized model of the atom introduced?
Answer: to overcome a major shortcoming of Rutherford's classical model

Question: In classical electrodynamics, a charge moving in a circle should do what?
Answer: radiate electromagnetic radiation

Question: Who modeled the atom in 1913, challenging Rutherford's model?
Answer: Niels Bohr

Question: What was predicted to happen to a nucleus-orbiting electron under Rutherford's model?
Answer: the radiation would cause it to lose energy and spiral down into the nucleus

Question: What statement did Bohr make about the electron of an atom, citing Planck's work?
Answer: an electron in a Bohr atom could only have certain defined energies
Title: Planck_constant

Bohr also introduced the quantity , now known as the reduced Planck constant, as the quantum of angular momentum. At first, Bohr thought that this was the angular momentum of each electron in an atom: this proved incorrect and, despite developments by Sommerfeld and others, an accurate description of the electron angular momentum proved beyond the Bohr model. The correct quantization rules for electrons – in which the energy reduces to the Bohr model equation in the case of the hydrogen atom – were given by Heisenberg's matrix mechanics in 1925 and the Schrödinger wave equation in 1926: the reduced Planck constant remains the fundamental quantum of angular momentum. In modern terms, if J is the total angular momentum of a system with rotational invariance, and Jz the angular momentum measured along any given direction, these quantities can only take on the values

Question: Who introduced the reduced Planck constant?
Answer: Bohr

Question: What is the reduced Planck constant also known as?
Answer: the quantity

Question: Who helped to give the correct quantization rules for electrons in 1925?
Answer: Heisenberg

Question: Who helped to give the correct quantization rules for electrons in 1926?
Answer: Schrödinger

Question: According to Heisenberg and Schrödinger, the reduced Planck constant remains what?
Answer: the fundamental quantum of angular momentum

Question: Bohr introduced what value as the quantum of angular momentum?
Answer: the reduced Planck constant

Question: What incorrect belief did Bohr hold about the reduced Planck constant?
Answer: Bohr thought that this was the angular momentum of each electron in an atom

Question: What scientist used matrix mechanics to bring electron behavior in line with the Bohr model?
Answer: Heisenberg

Question: When was the Schrödinger wave equation proposed?
Answer: 1926
Title: Planck_constant

where the uncertainty is given as the standard deviation of the measured value from its expected value. There are a number of other such pairs of physically measurable values which obey a similar rule. One example is time vs. energy. The either-or nature of uncertainty forces measurement attempts to choose between trade offs, and given that they are quanta, the trade offs often take the form of either-or (as in Fourier analysis), rather than the compromises and gray areas of time series analysis.

Question:  What measurable value obeys a similar rule of angular momentum?
Answer: time vs. energy

Question: What forces measurement attempts to choose between trade-offs, in quanta?
Answer: either-or nature of uncertainty

Question: What form do measurement attempt trade-offs for quanta take the form of?
Answer: either-or (as in Fourier analysis)

Question: How is uncertainly measured in this experience?
Answer: the standard deviation of the measured value from its expected value

Question: What type of analysis fits the either-or nature of the uncertainty?
Answer: Fourier analysis

Question: What example is given as another paired relationship of uncertainly related to standard deviation?
Answer: time vs. energy
Title: Planck_constant

The Bohr magneton and the nuclear magneton are units which are used to describe the magnetic properties of the electron and atomic nuclei respectively. The Bohr magneton is the magnetic moment which would be expected for an electron if it behaved as a spinning charge according to classical electrodynamics. It is defined in terms of the reduced Planck constant, the elementary charge and the electron mass, all of which depend on the Planck constant: the final dependence on h1/2 (r2 > 0.995) can be found by expanding the variables.

Question: What is the unit of magentic properties of the electron?
Answer: Bohr magneton

Question: What is the unit of magentic properties of atomic nuclei?
Answer: nuclear magneton

Question: The Bohr magneton is the magnetic moment of an electron under what restriction?
Answer: behaved as a spinning charge according to classical electrodynamics

Question: What three terms define the Bohr magneton value?
Answer: the reduced Planck constant, the elementary charge and the electron mass
Title: Planck_constant

In principle, the Planck constant could be determined by examining the spectrum of a black-body radiator or the kinetic energy of photoelectrons, and this is how its value was first calculated in the early twentieth century. In practice, these are no longer the most accurate methods. The CODATA value quoted here is based on three watt-balance measurements of KJ2RK and one inter-laboratory determination of the molar volume of silicon, but is mostly determined by a 2007 watt-balance measurement made at the U.S. National Institute of Standards and Technology (NIST). Five other measurements by three different methods were initially considered, but not included in the final refinement as they were too imprecise to affect the result.

Question: How was the Planck constant calculated in the early 20th century?
Answer: the Planck constant could be determined by examining the spectrum of a black-body radiator or the kinetic energy of photoelectrons

Question: The value quoted here for the Planck constant is based on a measurement in what year?
Answer: 2007

Question: Where was this measurement made?
Answer: the U.S. National Institute of Standards and Technology (NIST)

Question: What method was was used to obtain the measurement?
Answer: watt-balance measurement

Question: One other measure involved the molar volume of what element?
Answer: silicon
Title: Planck_constant

There are both practical and theoretical difficulties in determining h. The practical difficulties can be illustrated by the fact that the two most accurate methods, the watt balance and the X-ray crystal density method, do not appear to agree with one another. The most likely reason is that the measurement uncertainty for one (or both) of the methods has been estimated too low – it is (or they are) not as precise as is currently believed – but for the time being there is no indication which method is at fault.

Question: What is a main practical difficulty in determining n?
Answer: the two most accurate methods, the watt balance and the X-ray crystal density method, do not appear to agree with one another

Question: Why does this difficulty occur?
Answer: it is (or they are) not as precise as is currently believed

Question: Which method is at fault or the discrepancy?
Answer: there is no indication which method is at fault
Title: Planck_constant

The theoretical difficulties arise from the fact that all of the methods except the X-ray crystal density method rely on the theoretical basis of the Josephson effect and the quantum Hall effect. If these theories are slightly inaccurate – though there is no evidence at present to suggest they are – the methods would not give accurate values for the Planck constant. More importantly, the values of the Planck constant obtained in this way cannot be used as tests of the theories without falling into a circular argument. Fortunately, there are other statistical ways of testing the theories, and the theories have yet to be refuted.

Question: Other than the X-ray crystal density method, other methods rely on what two effects?
Answer: the Josephson effect and the quantum Hall effect

Question: Why does relying on these effects create concern?
Answer: If these theories are slightly inaccurate

Question: Using Planck constant values from these effects would lead to what logical issue?
Answer: a circular argument

Question: What is the saving grace of relying on these theories?
Answer: there are other statistical ways of testing the theories, and the theories have yet to be refuted.
Title: Planck_constant

A watt balance is an instrument for comparing two powers, one of which is measured in SI watts and the other of which is measured in conventional electrical units. From the definition of the conventional watt W90, this gives a measure of the product KJ2RK in SI units, where RK is the von Klitzing constant which appears in the quantum Hall effect. If the theoretical treatments of the Josephson effect and the quantum Hall effect are valid, and in particular assuming that RK = h/e2, the measurement of KJ2RK is a direct determination of the Planck constant.

Question: What is a watt balance?
Answer: an instrument for comparing two powers, one of which is measured in SI watts and the other of which is measured in conventional electrical units

Question: What value does RK represent?
Answer: the von Klitzing constant which appears in the quantum Hall effect

Question: If the effects are valid, for RK = n/e2, what is the measurement of KJ2RK equal to?
Answer: the Planck constant
Title: Planck_constant

The gyromagnetic ratio γ is the constant of proportionality between the frequency ν of nuclear magnetic resonance (or electron paramagnetic resonance for electrons) and the applied magnetic field B: ν = γB. It is difficult to measure gyromagnetic ratios precisely because of the difficulties in precisely measuring B, but the value for protons in water at 7002298150000000000♠25 °C is known to better than one part per million. The protons are said to be "shielded" from the applied magnetic field by the electrons in the water molecule, the same effect that gives rise to chemical shift in NMR spectroscopy, and this is indicated by a prime on the symbol for the gyromagnetic ratio, γ′p. The gyromagnetic ratio is related to the shielded proton magnetic moment μ′p, the spin number I (I = 1⁄2 for protons) and the reduced Planck constant.

Question: The gyromagnetic ratio is the constant proportion between the magentic field and what?
Answer: the frequency ν of nuclear magnetic resonance

Question: How does the water molecule impact the effect of magnetic fields on protons?
Answer: The protons are said to be "shielded" from the applied magnetic field by the electrons in the water molecule

Question: What three factors impact the gyromagnetic ratio?
Answer: related to the shielded proton magnetic moment μ′p, the spin number I (I = 1⁄2 for protons) and the reduced Planck constant.

Question: The gyromagnetic ratio is often difficult to determine due to difficulty accurately determining the value of what?
Answer: the applied magnetic field B
Title: Planck_constant

A further complication is that the measurement of γ′p involves the measurement of an electric current: this is invariably measured in conventional amperes rather than in SI amperes, so a conversion factor is required. The symbol Γ′p-90 is used for the measured gyromagnetic ratio using conventional electrical units. In addition, there are two methods of measuring the value, a "low-field" method and a "high-field" method, and the conversion factors are different in the two cases. Only the high-field value Γ′p-90(hi) is of interest in determining the Planck constant.

Question: How many methods of measuring the gyromagnetic ratio are there?
Answer: there are two methods of measuring the value

Question: How do conversion factors compare in "low-field" and "high-field" methods of measuring the gyromagnetic ratio?
Answer: the conversion factors are different in the two cases

Question: Which method is of interest in determining the Planck constant?
Answer: Only the high-field value Γ′p-90(hi) is of interest in determining the Planck constant

Question: Why is the measurement of electric current an issue in the estimate of the gyromagnetic ratio?
Answer: electric current: this is invariably measured in conventional amperes rather than in SI amperes
Title: Planck_constant

The Faraday constant F is the charge of one mole of electrons, equal to the Avogadro constant NA multiplied by the elementary charge e. It can be determined by careful electrolysis experiments, measuring the amount of silver dissolved from an electrode in a given time and for a given electric current. In practice, it is measured in conventional electrical units, and so given the symbol F90. Substituting the definitions of NA and e, and converting from conventional electrical units to SI units, gives the relation to the Planck constant.

Question: What is the Faraday constant?
Answer: the charge of one mole of electrons

Question: How is the Faraday constant determined?
Answer: by careful electrolysis experiments, measuring the amount of silver dissolved from an electrode in a given time and for a given electric current.

Question: How does the Faraday constant relate to the Planck constant?
Answer: Substituting the definitions of NA and e, and converting from conventional electrical units to SI units, gives the relation to the Planck constant.

Question: How is the Farday constant value quickly calculated?
Answer: the Avogadro constant NA multiplied by the elementary charge e
Title: Planck_constant

The X-ray crystal density method is primarily a method for determining the Avogadro constant NA but as the Avogadro constant is related to the Planck constant it also determines a value for h. The principle behind the method is to determine NA as the ratio between the volume of the unit cell of a crystal, measured by X-ray crystallography, and the molar volume of the substance. Crystals of silicon are used, as they are available in high quality and purity by the technology developed for the semiconductor industry. The unit cell volume is calculated from the spacing between two crystal planes referred to as d220. The molar volume Vm(Si) requires a knowledge of the density of the crystal and the atomic weight of the silicon used. The Planck constant is given by

Question: What is the primary method for determining the Avogadro constant?
Answer: The X-ray crystal density method

Question: The Avogadro constant is determined to be the ratio between what two factors in the X-ray crystal density method?
Answer: the volume of the unit cell of a crystal, measured by X-ray crystallography, and the molar volume of the substance

Question: What element is used typically to establish Avogadro's constant?
Answer: Crystals of silicon

Question: How is unit cell volume calculated?
Answer: from the spacing between two crystal planes referred to as d220

Question: Calculating molar volume requires knowledge of what two factors?
Answer: the density of the crystal and the atomic weight of the silicon used
Title: Planck_constant

There are a number of proposals to redefine certain of the SI base units in terms of fundamental physical constants. This has already been done for the metre, which is defined in terms of a fixed value of the speed of light. The most urgent unit on the list for redefinition is the kilogram, whose value has been fixed for all science (since 1889) by the mass of a small cylinder of platinum–iridium alloy kept in a vault just outside Paris. While nobody knows if the mass of the International Prototype Kilogram has changed since 1889 – the value 1 kg of its mass expressed in kilograms is by definition unchanged and therein lies one of the problems – it is known that over such a timescale the many similar Pt–Ir alloy cylinders kept in national laboratories around the world, have changed their relative mass by several tens of parts per million, however carefully they are stored, and the more so the more they have been taken out and used as mass standards. A change of several tens of micrograms in one kilogram is equivalent to the current uncertainty in the value of the Planck constant in SI units.

Question: What measurement is deemed most important to redefine in terms of physical constants?
Answer: the kilogram

Question: What is the shape of the object that establishes the base unit of the kilogram?
Answer: cylinder

Question: What alloy is the base unit of the kilogram made from?
Answer: platinum–iridium

Question: Where is the base unit for the kilogram kept?
Answer: in a vault just outside Paris
Title: Planck_constant

The legal process to change the definition of the kilogram is already underway, but it had been decided that no final decision would be made before the next meeting of the General Conference on Weights and Measures in 2011. (For more detailed information, see kilogram definitions.) The Planck constant is a leading contender to form the basis of the new definition, although not the only one. Possible new definitions include "the mass of a body at rest whose equivalent energy equals the energy of photons whose frequencies sum to 7050135639273999999♠135639274×1042 Hz", or simply "the kilogram is defined so that the Planck constant equals 6966662606895999999♠6.62606896×10−34 J⋅s".

Question: Where would the decision to change the definition of the kilogram have occured at the earliest?
Answer: the General Conference on Weights and Measures in 2011

Question: Was the Planck constant the only option for redefining the kilogram?
Answer: The Planck constant is a leading contender to form the basis of the new definition, although not the only one

Question: The mass of a resting body with what energy would be equal to a kilogram?
Answer: 7050135639273999999♠135639274×1042 Hz

Question: A kilogram could be definined as having a Planck constant of what value?
Answer: 6966662606895999999♠6.62606896×10−34 J⋅s
Title: Comcast

Comcast Corporation, formerly registered as Comcast Holdings,[note 1] is an American multinational mass media company and is the largest broadcasting and largest cable company in the world by revenue. It is the second largest pay-TV company after the AT&T-DirecTV acquisition, largest cable TV company and largest home Internet service provider in the United States, and the nation's third largest home telephone service provider. Comcast services U.S. residential and commercial customers in 40 states and the District of Columbia. The company's headquarters are located in Philadelphia, Pennsylvania.

Question: What is the largest cable company in the world by revenue?
Answer: Comcast Corporation

Question: What merged companies are the largest pay TV entity in the world?
Answer: AT&T-DirecTV

Question: Comcast is also the largest media company in the United States in what broadband area?
Answer: Internet service provider

Question: In what areas of the US does Comcast operate?
Answer: 40 states and the District of Columbia

Question: Where is Comcast company headquarters?
Answer: Philadelphia, Pennsylvania
Title: Comcast

Comcast operates multiple cable-only channels (including E! Entertainment Television, the Golf Channel, and NBCSN), over-the-air national broadcast network channels (NBC and Telemundo), the film production studio Universal Pictures, and Universal Parks & Resorts, with a global total of nearly 200 family entertainment locations and attractions in the U.S. and several other countries including U.A.E., South Korea, Russia and China, with several new locations reportedly planned and being developed for future operation. Comcast also has significant holding in digital distribution (thePlatform). In February 2014 the company agreed to merge with Time Warner Cable in an equity swap deal worth $45.2 billion. Under the terms of the agreement Comcast was to acquire 100% of Time Warner Cable. However, on April 24, 2015, Comcast terminated the agreement.

Question: What are some of the cable TV networks owned by Comcast?
Answer: E! Entertainment Television, the Golf Channel, and NBCSN

Question: What two national over-the-air broadcast entities are owned by Comcast?
Answer: NBC and Telemundo

Question: Comcast owns what movie studio?
Answer: Universal Pictures

Question: What company did Comcast propose a merger with?
Answer: Time Warner Cable

Question: What date did Comcast drop their proposed merger agreement with Time Warner?
Answer: April 24, 2015