bluuebunny/crossref_metadata_2025 huggingface dataset:
Physics in Engineering
Authors: Houston W. V.
Published: August 2005

The application of discoveries made in pure science to engineering problems is described and illustrated by incidents in the history of submarine telegraph cables, radio communication, and electronics.
Acoustic Doppler Effect and Phase Invariance
Authors: Spees A. H.
Published: August 2005

Attention is called to the usefulness of the Doppler effect in introducing the idea of invariance with respect to coordinate transformation. The invariant property of the phase of a sound wave with respect to Galilean transformation is applied to several Doppler effects including that resulting from transverse motion of source and detector in a moving medium.
Demonstrations of Electromagnetic Waves in Helices
Authors: Andrews C. L.
Published: August 2005

Demonstrations of standing microwaves in helices are described for helix circumferences ranging from 0.1 to 3 wavelengths. Special attention is given to dimensions of helices used in (1) traveling wave tubes as broad band amplifiers, (2) axial mode antennas for producing a circularly polarized axial beam, and (3) radial mode antennas for broadcasting a horizontally polarized radial beam. The demonstrations are made with 2450 megacycle/sec educational equipment.
Proof of the Expression (E/ρ)12 for the Velocity of Sound by Use of an Equality of Energies
Authors: Sleator W. W.
Published: August 2005

An argument is presented by which the velocity equation for sound waves in a gas is obtained as a result of equating the kinetic and potential energies per unit volume at the same time and position in the wave train.
Consequences of Parameter Invariance in Geometrical Optics
Authors: Penfield R. H.
Published: August 2005

In the electromagnetic theory one hears of gauge invariance and the difficulties that result from this. Similar obstacles arise in the general theory of relativity because of the coordinate covariance requirement. The actual nature of the effect of the invariance stipulations is usually not clearly understood because the theories investigated are themselves rather complicated. However, it is possible to pick a simple enough example so that one can clearly see the effect of invariance requirements. It is the purpose of this paper to pick a central problem of geometrical optics and to show what happens as a result of the parameter covariance.
Reproductions of Prints, Drawings, and Paintings of Interest in the History of Physics. 71. The Main Entrance Doors of Imperial Chemical House, Millbank, London
Authors: Watson E. C.
Published: August 2005

The magnificent metal doors of Imperial Chemical House, Millbank, London, deserve to be better known to physics teachers than they are. They are faced by six cast panels illustrating the evolution of civilization as a result of scientific discoveries. Two of these panels are here reproduced and discussed.
Measurements with a Modified Schilling Sound Apparatus
Authors: Hoyt Rosalie C.
Published: August 2005

A commercial electrostatic speaker is now available that provides an excellent and cheap line source of high-frequency sound in the 1000 cps to 20 000 cps range. It can also be operated in reverse to act as a quite satisfactory detector at these frequencies. By replacing the Galton whistle with one of these speakers, and using a second speaker as a detector, the Schilling apparatus can be used for quantitative undergraduate experiments on interference and diffraction, yielding results to better than 2% accuracy.
Scalar Field Theory as a Theory of Gravitation. I
Authors: Bergmann Otto
Published: August 2005

A Lorentz-invariant theory of gravitation is examined in which the field variable is a scalar in the sense of the four-dimensional tensor calculus. The Kepler-motion has the same form as in Nordström's theory and differs accordingly from the vector theory. The perihelion motion is of the same absolute value as in the vector theory, and hence much too small in comparison with the experimental value for the planet Mercury, and moreover of the wrong sign. The influence of radiation damping is discussed in a second paper which will be published shortly.
Demonstration in Static Electricity
Authors: Cunningham R. G. , Montgomery D. J.
Published: August 2005

A set of nylon or other textile filaments, supported by a pair of standoff insulators, can be used to demonstrate the effects of static electricity. Several methods of charging and discharging the filaments are described.
Ferrimagnetic Resonance and Some Related Effects
Authors: Wangsness Roald K.
Published: August 2005

The semiclassical resonance theory for a system of coupled magnetic sublattices is briefly reviewed and some similarities and differences of ferromagnetic and ferrimagnetic resonance considered. The use of the effective gyromagnetic ratio simplifies the interpretation of many experimental results for g-values. The qualitative application of this concept to some related phenomena shows that they can have features characteristic of the ferrimagnetic case.
Experiment on the Mechanics of Atomic Collisions
Authors: Barkow Arthur G.
Published: August 2005

A chosen event in a nuclear emulsion is used as the basis of an experiment in a course in modern physics for seniors. It is one of a group of experiments designed to illustrate atomic interactions that has stimulated keen interest among students in nuclear plate work.
Hydromagnetism. II. A Review
Authors: Elsasser Walter M.
Published: August 2005

The theoretical foundations having been given in Part I, phenomena here reviewed are: character and magnitude of the geomagnetic secular variation, the geomagnetic westward drift, hydromagnetic interpretation of irregularities in the earth's angular velocity; nature of fossil magnetism, magnetization of historical and prehistorical bricks and clays, of eruptive and sedimentary rocks, reversals of the earth's field in the geological past, evidence for pole migration; exploration of solar magnetic fields, the solar convection zone, magnetic fields of sunspots, the sunspot cycle, the over-all solar field, observations of magnetic stars, variable magnetic stars; fields in the solar corona, streamers and prominences, magnetic storms and auroras, planetary fields, the galactic field, the problem of cosmic rays.
Electromagnetic Induction in Moving Systems
Authors: Corson Dale R.
Published: August 2005

The principles underlying the extension of the Maxwell equation curlE = −∂B/∂t to moving media are discussed, and illustrations with specific moving systems are presented. The principles are applied to the case of the unipolar generator.
Ultrasonic Propagation in Liquid Helium
Authors: Chase C. E.
Published: August 2005

A series of measurements of the propagation of sound in liquid helium are described, and the results discussed in terms of various aspects of the theory of liquid helium. Measurements of the velocity were first made at 14.2 mc/sec over the temperature range from the normal boiling point down to 1.2°K, with particular attention to the low-temperature region and the neighborhood of the λ point. The attenuation was later measured at 2.0, 6.0, and 12.1 mc/sec, and the measurements were extended down to 0.85°K. A few velocity measurements were also made at these frequencies. Finally the 12.1 mc/sec results were extended down to 0.1°K by the technique of adiabatic demagnetization. The attenuation in helium II is anomalously high and passes through two closely spaced maxima a little below 1°K, finally falling smoothly toward zero at the absolute zero. No adequate theoretical explanation for this behavior exists, although above 1°K the high attenuation has been explained qualitatively. Near the λ point the attenuation rises to another very sharp maximum and the velocity passes through a minimum. This behavior sheds some light on the nature of the λ transition. The first part of this paper is devoted to a brief review of relevant experimental and theoretical aspects of the liquid helium problem.
Criteria for the Consistent Counting of Delta Rays on Heavy Nuclear Tracks in Emulsion Plates
Authors: Young Otis B. , Ballowe William C.
Published: August 2005

This paper is an attempt to improve greatly the consistency of delta-ray counting along tracks of heavy nuclei in emulsions. The problem is complicated and, unless satisfactory criteria are properly followed, variable results may be expected both from a given scanner and from different scanners. A set of criteria are given. Considerable information regarding their use is included. This work is adapted to nuclei with Z's of ten or greater.
Rationalized mks System of Units
Authors: Chapman Seville
Published: August 2005

The mks system of units is explained and compared with the Gaussian system (and its components, the cgs electrostatic system and cgs electromagnetic system). It is suggested that the mks system is the easier system to use. Symbols, dimensions, units, and equivalents are given for the most important electric and magnetic quantities. Many of the more common equations are written in both systems, and a simple scheme for conversion is presented.
Precision for a Pittance
Authors: Michels Walter C.
Published: August 2005

Apparatus consisting of two precision potential dividers, a student's galvanometer, a cheap standard cell, a table radio receiver, and a pair of intermediate frequency transformers is shown to be sufficiently flexible and sufficiently precise to allow it to be used for a large part of the electrical calibrations needed in a laboratory. Accuracies of about 14 of 1% at zero frequency and of about 1% at 455 kilocycles per second can be obtained. The total cost of the equipment is $125 or less.
Inductive and Capacitive Reactance
Authors: Albert E. G.
Published: August 2005

A method of determining from a vector diagram the inductive reactance of an inductor in terms of the circuit constants and for determining the capacitive reactance of a capacitor also in terms of circuit constants is explained. The plan is to consider a uniform circular motion point in its path around a circle of a properly chosen dimension radius vector and to compare the speed of the uniform circular motion point with the speed of its simple harmonic projection point moving along the vertical axis.
On Coherence Properties of Light Waves
Authors: Forrester A. T.
Published: August 2005

The electric field of a luminous region is much more regular than is generally realized. Phases vary periodically and predictably, and the nature of the polarization remains approximately constant, for times of the order of the reciprocal of the line width in cycles per second. In a plane at right angles to the mean direction of propagation the light wave is coherent over an area approximately λ2/Ω, where Ω is the solid angular spread in the light. These ideas, when applied to the problem of producing beats between lightwaves, lead to a signal amplitude which has been verified experimentally.
Mesons and Hyperons
Authors: Shapiro Maurice M.
Published: August 2005

Basic properties of L-mesons, K-mesons, and hyperons are summarized in the light of evidence available in mid-1955. Masses, decay schemes, lifetimes, and Q-values are tabulated. The accompanying notes describe how “best values” were arrived at, and serve as a guide to a representative selection of references on unstable particles.
Inverted Soap Bubbles—A Surface Phenomenon
Authors: Skogen N.
Published: August 2005

By pouring soap water onto a surface of soap water it is possible to produce thin spherical shells of air in the water (inverted soap bubbles). The largest diameter observed is about 20 mm. Interference colors indicate shell thickness of the order 0.001 mm. Lifetimes of the bubbles of 4–5 minutes have been observed. A connection between the inverted bubbles and drops of water swimming on the surface is pointed out.
Monochromatic Approximation of Blackbody Radiation
Authors: Shanks D.
Published: August 2005

An approximate theory of blackbody radiation is given which is not correct quantitatively and therefore cannot be taken too seriously. Nonetheless its extreme simplicity and moderate accuracy gives it a number of didactic and intuitional advantages. The Wien displacement and Stefan-Boltzmann radiation laws are deduced very simply. The exponent of T in the latter is seen to be the number of dimensions of space-time, that is, four. A simple formula for Avogadro's number, N = PV/pv, is derived and discussed.
Production of Atomic Displacements by High-Energy Particles
Authors: Brinkman J. A.
Published: August 2005

The processes by which atoms in solids are displaced from their normal positions by high-energy neutrons, cyclotron particles, and electrons are discussed. A radiation damage model is presented which involves two basic features: (1) the production of interstitial atoms and vacant lattice sites, and (2) the production of displacement spikes. These two concepts are sufficient to account for most of the observed property changes resulting from atomic displacement by high-energy particles. Some of the experimental results which provide the most direct support for these concepts are presented.
Survey of the Interpretations of Quantum Mechanics
Authors: Bunge Mario
Published: August 2005

A survey is made of the hitherto proposed answers to the following crucial questions arising in the physical interpretation of the mathematical formalism of wave mechanics: (I) What is the meaning of the dynamical variables and of their eigenvalues? (II) What is the meaning of the wave function? (III) What is the nature and origin of Heisenberg's uncertainty relations? (IV) What is the nature of the systems dealt with by wave mechanics? Taking into account the interpretations that have been proposed in the last few years, a surprisingly large number of answers is found. The present situation in quantum mechanics is compared with similar crises in the past history of physics. The mere multiplicity of consistent interpretations of quantum mechanics is regarded as a warning against the dogmatic adherence to any one of them, to the exclusion of new possibilities.
Infrared Radiation in the Atmosphere
Authors: Plass Gilbert N.
Published: August 2005

The infrared radiation flux in the atmosphere is determined by the distribution of three gases—water vapor, carbon dioxide, and ozone. The general equations for the transfer of radiation in a gas are derived. These equations are solved for four simple model atmospheres that illustrate various features of the more complicated results for the earth's atmosphere. The atmospheric infrared radiation flux can be calculated from laboratory absorption measurements. The results of such calculations are discussed in detail for the frequency ranges that are influenced by the carbon dioxide and ozone bands.
Where Do We Get the Teachers?
Authors: Henry David D.
Published: August 2005

Estimates of the requirements for new teaching personnel in colleges and universities indicate that a serious shortage is impending within the decade 1960–1969. Measures currently being practiced are inadequate to fill the need. A more active recruitment and training program on the part of universities is advocated. The obligation of industry to avoid undermining educational programs by recruiting staff members away from colleges and universities is emphasized.
Summer Institutes for High School Science Teachers
Authors: Weber Robert L.
Published: August 2005

Increasing college enrollments, and the needs of both industry and the national welfare for capable, technically trained personnel emphasize the desirability of special supplemental programs for increasing the competence of high school teachers of science and mathematics. The growth of interest in summer science institutes, their financial support, and their effectiveness are discussed.
Measurement of Velocity of Sound in Gases
Authors: Bancroft Dennison
Published: August 2005

A method of determining the velocity of sound by observing the frequencies of radial oscillation of a gas confined in a spherical cavity is described. The accuracy appears to be comparable with that of the best methods available to date. A few preliminary results are quoted for argon, oxygen, and CO2. The possibility of utilizing the measurements for determination of the absolute temperature of the ice point is discussed.
X-Ray Equipment for the Atomic Physics Laboratory
Authors: Hilton Wallace A. , Clayton Glen T.
Published: August 2005

Equipment using obsolete medical x-ray machines to perform the basic x-ray absorption and diffraction experiments for the undergraduate atomic physics laboratory is described.
Some Interesting Cases of Vibrating Systems
Authors: Bartunek Paul F.
Published: August 2005

Three simple vibrating systems are described: The bifilar and trifilar pendula and the meter stick rocking on a cylindrical surface. All types afford challenging analytical problems. The bifilar pendulum with adjustable height of bob gives practice in scientific judgment, for of three possible modes of oscillation one is definitely best if one be interested in determination of g. The dumbbell model of bifilar pendulum, as well as the rocking stick, offer opportunities to study the effect of separately changing inertia and restoring factors. The trifilar pendulum offers an alternate to other common methods of measuring moments of inertia.
Experiments on Viscoelasticity
Authors: Ivey Donald G.
Published: August 2005

The propagation of sound waves in rubber strips is used to illustrate visco-elastic behavior. The experiments introduce time-dependent mechanical properties of solids at a level suitable for use in undergraduate laboratories.
Classical Meson Theory. II
Authors: Kahana S. , Coish H. R.
Published: August 2005

Classical meson theory, to which an elementary introduction is given in part I, is applied to nuclear forces, the deuteron, meson scattering, and photoproduction.
New System of Physical Units and Standards
Authors: Ludovici Bruno F.
Published: August 2005

The present system of physical units and standards is critically examined with a view of the possible destruction of the present primary standards through a natural catastrophe. A new system is proposed.
Reproductions of Prints, Drawings, and Paintings of Interest in the History of Physics. 76. An Early Meteorological Observatory and Town Clock
Authors: Watson E. C.
Published: August 2005

The Tower of Winds in Athens, built about 100 B.C. by the Greek astronomer, Andronicus of Cyrrhus, is probably the oldest meteorological observatory and town clock still standing. A careful study of this structure was made at the middle of the eighteenth century by James Stuart and Nicholas Revett, a portion of which is here reproduced.
Quaternions as 4-Vectors
Authors: Walker Marshall J.
Published: August 2005

The development of the algebra of quaternions is reviewed and discussed from a modern viewpoint stressing their aspect as 4-vectors and their educational value to the student of physics. Their relationship to 3-vectors, tensors, and complex matrices is noted. Geometrical visualization of their properties is developed. Their application to problems of polarized radiation and special relativity is described.
Thermodynamic Theory of Irreversible Processes. II. Sedimentation Equilibrium of Fluids in Gravitational and Centrifugal Fields
Authors: Miller Donald G.
Published: August 2005

Using results of the thermodynamic theory of irreversible processes, general equations are given for the transport of all charged and uncharged constituents of a multicomponent fluid situated in a gravitational or centrifugal field. From these equations, relations describing the special case of sedimentation equilibrium are derived. It is pointed out that the Onsager relations are not required in this case. Different integration paths lead to certain useful exact equations, one of which has been given recently by Young, Kraus, and Johnson. These equations may be used to obtain from sedimentation experiments (1) the activity as a function of the pressures and compositions associated with sedimentation equilibrium; (2) the activity as a function of composition at a given pressure if it is known at one composition and the same pressure and if partial molal volume and density data are known as a function of P; (3) the activity as a function of pressure for one composition if it is known as a function of composition at a single pressure, and conversely.
Scattering of Classical Electrons by Nuclei
Authors: Heims S. P. , Ravenhall D. G. , Yennie D. R.
Published: August 2005

In connection with recent research at Stanford on the scattering of high-energy electrons by atomic nuclei, a study is made of the scattering of extremely relativistic classical charged particles by a distribution of charge. The approximation is made that the mass of the scattered particle can be neglected; this is valid for the energies used in the experiments (between 100 and 200 Mev). In the case of the point charge there appear orbits in which the particle encircles the nucleus many times before emerging. Cross sections are obtained for this case, for the spherical shell, and for the “smoothed uniform” charge distribution. From these results it is clear that the experimentally interesting region is completely inaccessible to classical particles, and that the process observed corresponds more to the diffraction of waves.
Development of the Maxwell-Lorentz Equations from Special Relativity and Gauss's Law
Authors: Frisch David H. , Wilets Lawrence
Published: August 2005

Maxwell's equations and the Lorentz force law are developed by applying the transformations of special relativity to Gauss's law on the flux of the electric field, ∫E · dS = 4πqenclosed, provided that electromagnetic signals are propagated with the speed of light, and that the electric force on a test charge is velocity-independent and does not depend on time derivatives of the source position of order higher than the acceleration.
Interference in an Optical Wedge
Authors: Oppenheim Uri , Jaffe Joseph H.
Published: August 2005

Many standard textbooks treat interference in an optical wedge quite inadequately. Elementary treatments of this problem often leave much confusion about the exact conditions under which the fringes are formed and observed. Here a unified introductory treatment is presented both for two-beam and multiple-beam interference. Special attention is given to the localization of the fringes around the wedge. Factors governing the fringe visibility are examined.
Matrix Representation of Thermodynamic Fundamentals
Authors: Kyame Joseph John
Published: August 2005

The use of matrices for representing fundamental thermodynamic relations is demonstrated. Maxwell's relations and other thermodynamic derivatives are readily obtained by differentiation of the matrices defined.
Authoritarianism versus Imagination in Physics Teaching
Authors: Michels Walter C.
Published: August 2005

The failure of our educational system to produce as many physicists as are required for the national welfare challenges us to re-examine our introductory college physics courses. If one accepts the tenable idea that physics is a research activity, rather than a body of knowledge, he finds much to criticize in the aims and methods of these courses. Some changes which might help to remedy the faults of the traditional course are proposed and their advantages and disadvantages are discussed. Greater emphasis on the encouragement of independent thought is urged.
Suggestion Regarding the Introduction of the Concept of Phase Change for Reflected Radiation
Authors: Cook C. Sharp
Published: August 2005

In the study of radiation reflected from a surface, the concept of phase change appears to many students as some sort of “black magic” when introduced following the derivation of the Fresnel equations. This, however, is the point at which the concept is first considered by many texts. It seems that by appropriate introduction of phase change into the derivation of the Fresnel equations, a clearer understanding of this concept may be gained.
Science and Engineering Education
Authors: Adler Richard B.
Published: August 2005

A discussion of the appropriate place of science, and especially of physics, in engineering education and in general education; and of a university education in our present technological society.
Experiment on Velocity and Acceleration Using an Automobile
Authors: Baez Albert V.
Published: August 2005

An experiment is described in which measurements of time, distance, and speed made in an automobile yield data which can be plotted graphically to clarify motions of displacement, velocity, and acceleration.
Reminiscences of the Early Years of the Association
Authors: Webster David L.
Published: August 2005

Events and conditions leading to the founding of the Association are recounted here; also some of the objectives and accomplishments of its founders, Dodge and Klopsteg, and of some of its other pioneers, especially Roller and Richtmyer; and some of Richtmyer's statements about the art of teaching physics are quoted with approval.
Electrostatic Potential in Crystals
Authors: Callen Earl
Published: August 2005

The electronic potential distribution at the surface of a crystal is described. The periodic potential of the interior is modified at the surface by a redistribution of charge, which may be developed in terms of a number of related dipole double layers, space charge, and net surface charge. The image, exchange, and correlation fields, and the field of the net surface charge are presented. The relationship of these effects to the work function of metals and nonmetals, and their role in rectification in metal-semiconductor contacts is mentioned.
Radiation Minimum Temperatures
Authors: Davis Francis K.
Published: August 2005

Frost resulting from cooling of vegetation by nocturnal radiation is a serious agricultural problem. Because of the number of variables involved, attacks on this problem from a purely theoretical point of view have met with only moderate success. It seems logical to suppose that an instrument might be devised which would speed up the natural radiation processes and enable an observer to obtain in a few hours a measure of the cooling which occurs naturally over a period of 12 to 14 hr. Such an instrument could serve as a frost warning device. This paper describes the construction of a radiation device and presents experimental evidence to show that it can be used as a predictor of freezing temperatures at vegetation level.
Interpreting Chladni Figures
Authors: Waller Mary D.
Published: August 2005

Jensen's recently published Chladni figures can be interpreted as normal modes of vibration with antinodal centers which are distorted by the experimental method employed to produce them. Thefree transverse vibrations of uniform plates always conform with the symmetry of the geometrical surfaces. The principle of symmetry and of corresponding vibrations enables them to be identified and arranged in a systematic manner. The solid carbon dioxide method of exciting free vibrations, supplemented by the bow, produces the most symmetrical figures.
Descriptive Theory of Semiconductors
Authors: Steele Earl L.
Published: August 2005

A nonmathematical description of the basic ideas and concepts underlying the field of semiconductors and semiconductor devices is given here. The role of the energy band scheme, of the impurity donor and acceptor atoms, and of the p-n junction in semiconductor device physics is discussed in detail. The nonsymmetrical conduction or rectification properties of the p-n junction, which determine such things as forward and reverse voltage-current relationships, are qualitatively treated. The p-n junction theory is then extended to the physics of transistor action and to a discussion of the fundamental parameters which enter into transistor behavior.
Some Recent Determinations of the Velocity of Light. II
Authors: Mulligan Joseph F. , McDonald Daniel F.
Published: August 2005

Four methods developed during the past five years for the determination of the velocity of light in vacuo are reviewed. These include coincidence-counter determinations of gamma-ray velocities, band-spectra methods, Froome's microwave interferometer, and Florman's radiofrequency interferometer. The results of recent repetitions of Bergstrand's geodimeter measurement of c are also summarized. The best measurements by a variety of techniques yield a weighted average of 299 792.8 km/sec for c, with a probable error of ±0.2 km/sec. A reasonable limit of error of ±0.6 km/sec is recommended. Some reasons for the low values of c obtained previously by optical techniques are discussed.
Reconstruction in Physics
Authors: Bushkovitch A. V.
Published: August 2005

It is suggested that, under the stimulus of the current criticisms by engineers, the teaching of physics be drastically modernized. Two attempts in this direction at Saint Louis University are described: one is the introduction of five weeks of modern physics into the second year of the two-year Engineering Physics course, and the other, an undergraduate (senior) course in Relativity and Quantum Mechanics.
On Teaching College Science Teachers to Teach
Authors: Süsskind Charles
Published: August 2005

A number of suggestions is made regarding the training of graduate students in science for a college-teaching career. The principal method recommended comprises a formal course in which teaching abilities can be evaluated and sharpened.
Unified Treatment of the Vibrating Arm
Authors: McLachlan Dan
Published: August 2005

This paper presents a method of solving certain differential equations of physics in a manner that aids the physics student to grasp the relationships between several of the functions with which he is already familiar. The method of making the relationships apparent is based on the use of one procedure for deriving the circular functions, hyperbolic functions, and elliptical functions as well as others that are less common. While the method herein presented has a certain amount of generality, it is restricted to various types of force functions and does not include friction, induction, or driving forces. The physical illustration is a single vibrating mass and no discussion is given of vibrating strings or membranes.
Unified Treatment of the Vibrating Arm. Part II. The Solution When the Restoring Force Is Positive and Also When It Is Expressed as a Power Series in ψ
Authors: McLachlan Dan
Published: August 2005

This second part carries on with the principles illustrated in Part I. Again nothing new is presented except a unified viewpoint. Three main subjects are discussed: A. Nonperiodic systems; B. The restoring force as a power series in ψ; and C. Methods for testing the validity of a solution. The discussion leads to interesting and familiar subjects such as hyperbolic and elliptical functions.
Concentration and Size of Photons from Particle Interpretation of Blackbody Radiation
Authors: Magram Sidney J.
Published: August 2005

In the Planck radiation law the expression for energy density between λ and λ+dλ may be divided by hc/λ to give an expression for the number of photons per unit volume as a function of λ. It is shown that N = 20.30 cm−3 deg−3 T3, where N is the number of photons per cm3. The expressions λnT = 0.3669 cm deg and λaT = 0.5326 cm deg are derived, where λn is the wavelength at which the number of photons per unit volume between λ and λ+dλ is a maximum and λa is the wavelength associated with the photon of average energy. The average energy per photon is EAv = 2.701 kT.
Quantitative Relationships for Charged Inflated Balloons
Authors: Baez Albert V.
Published: August 2005

Charged, inflated, lighter-than-air rubber balloons moored by strings form a useful electroscope which can be viewed by a large audience. The balloons are out of the demonstrator's way and are not attracted to him or to other equipment. A calculation and a graph are given which permit the device to be used as a crude electrometer capable of detecting charges smaller than a microcoulomb.
Demonstration of Electron and Hole Injection in Alkali Halides
Authors: Hersh Herbert N. , Bronstein Leonard
Published: August 2005

A simple experimental setup, well adapted for demonstration purposes for the beginner and advanced student alike, vividly depicts current flow in insulators by holes or electrons. This is achieved by the trapping of carriers during electron or hole injection in alkali halides giving rise to striking color changes due to the formation of color centers.
Sewing-Needle Proportional Counter
Authors: Benade A. H. , Chrien R. E.
Published: August 2005

A simple proportional counter made from common materials, and supplied with high voltage by a circuit made from automotive ignition parts, is described and investigated. Alpha particles from Po210 are shown to give up to 25-volt pulses, while beta rays from Cs137 produce signals with amplitudes up to 2 volts without the use of any external amplification. These pulses are readily heard with headphones, or amplified by standard public-address equipment.
On the Relations between Light and Electricity
Authors: Watson E. C.
Published: August 2005

The purpose of this article is to celebrate the centenary of the birth of Heinrich Rudolf Hertz by reprinting his famous lecture on the relations between light and electricity delivered before the German Association for the Advancement of Natural Science and Medicine at Heidelberg on September 20, 1889.
Presentation of Mark W. Zemansky as 1956 Oersted Medalist
Authors: Palmer R. Ronald
Published: August 2005

Remarks made by the Chairman of the Committee on Awards for 1956 in presenting the medalist for the Oersted Medal, awarded to Mark W. Zemansky, Professor of Physics at The City College, New York, in recognition of notable contributions to the teaching of physics.
Introductory Experiment in Electrical Measurements
Authors: Worrell Francis T.
Published: August 2005

The author has felt that the transition from the elementary to the intermediate laboratory may sometimes be too abrupt, and that while the student is getting accustomed to the more advanced laboratory he misses some of the important points in the early experiments he performs. The experiment described is designed to accustom the student to the new level of experiments, and give him some insight into some fundamental principles of experimentation. The experiment consists of measuring a resistance by several different methods. The results are then compared, and the relative merits of the methods are discussed. The methods used are the ohmmeter, the voltmeter-ammeter method, the Wheatstone bridge, the potentiometer, and the substitution method. Details of these measurements will be discussed.
Scholarship Awards Program of the Chesapeake Section
Authors: Watson Bernard B.
Published: August 2005

The Scholarship Awards Program of the Chesapeake Section, AAPT, is described giving details on the planning and arrangements for the program, initiated in the 1955–1956 academic year and open to seniors in over 800 secondary schools in Delaware, Maryland, Virginia, and the District of Columbia. Some problems which have arisen in connection with the program are discussed.
Syllabus for the One-Year College Course in Physical Science
Authors: Holton Gerald
Published: August 2005

Prepared at the request of the AAPT Conference to illustrate how the recommendations of its Report may be implemented, this syllabus describes a physical science course for students not intending to major in that field.
Three-Semester Introductory Course for Engineers and Science Majors
Authors: Whaley R. M.
Published: August 2005

Prepared at the request of the AAPT Conference to illustrate how the recommendations of the Report may be applied in a large university, this syllabus describes a three-semester course for engineers and science majors.
Elementary Physics Laboratory Instruction at the Massachusetts Institute of Technology
Authors: Brown Sanborn C.
Published: August 2005

A survey of the laboratory objectives and teaching methods is given. Specific examples of the type of elementary laboratory experiments used are presented.
Reciprocity Calibrations
Authors: Ackerman Eugene , Holak William
Published: August 2005

The reciprocity technique is used currently for primary microphone calibrations. The theory of this technique is developed in this article in a form suitable for physics students; it can be used as the basis of advanced experiments. Two types of reciprocity are first discussed. One, the electromechanical, applies to many practical transducers. The other, the acoustic reciprocity, is shown to be a special case of Green's theorem. One application is discussed. These two types of reciprocity are combined to derive the electroacoustic reciprocity constant. Finally, a method is outlined of using the electroacoustic reciprocity constant for primary microphone calibrations using only conveniently measured quantities.
Simplified Theory of Ship Waves
Authors: Keith H. D.
Published: August 2005

The physical significance of group velocity is considered critically and a general and realistic definition given. This is used to develop a simple phenomenological theory of the ship wave pattern including the prediction of phase changes at singularities, and the variation of the wave-making resistance of a ship with speed is shown to be governed in a simple way by the interference of bow and stern waves.
Marian Smoluchowski and the Theory of Probabilities in Physics
Authors: Ulam S.
Published: August 2005

A brief account of the life of the Polish physicist Marian Smoluchowski, with some observations on the implications of his scientific work.
Neglected Quadrupole
Authors: Arfken George
Published: August 2005

The usual textbook developments of the electric dipole potential are discussed and the limitations, some inherent and some arbitrary, are noted. Introducing Legendre polynomials by their generating function an alternate derivation is presented. This latter approach offers the double advantage of introducing the undergraduate to quadrupoles and higher multipoles and providing him with a powerful mathematical tool for treating electrostatic and many other problems. The importance of the quadrupole concept in modern physics is emphasized.
Heat Bridge for Measuring Thermal Conductivity
Authors: Landegren G. F.
Published: August 2005

An experimental apparatus for measuring thermal conductivity of solid materials is described which is analogous to the Wheatstone bridge for measuring electrical resistance.
Theory of the Relativistic Oscillator
Authors: MacColl L. A.
Published: August 2005

This is a study of the motions of a particle subject to the restoring force exerted by a linear spring, under the assumption that the mass depends upon the speed according to the formula given by the theory of special relativity.
Electrification of Aerosols by Ionic Diffusion
Authors: Gunn Ross
Published: August 2005

The distribution of free electrical charges transferred to cloud droplets by ionic diffusion provides an illuminating example of a simple statistical process. Tables are constructed from first principles, shown to agree with successive terms of the binomial point equation of statistics, and applied to the initial stages of droplet electrification. The final equilibrium distribution, described by the basic electrification equation for aerosols, corresponds to an equipartition between the electrostatic energy of the droplets and their thermal kinetic energy.
Paradox of the Twins
Authors: Frye Royal M. , Brigham Virginia M.
Published: August 2005

There is no ambiguity about the relationship between time and motion, either in terms of experiments with rapidly moving mesons or canal rays, or in terms of general relativity theory. But contradictory results are obtained when it is attempted to make computations using only the special relativity theory. A number of opinions to the contrary have recently found their way into print.
Basic Concepts of Ultrasonic Interferometry in Liquids
Authors: Carome E. F. , Gutowski F. A. , Schuele D. E.
Published: August 2005

The use of the acoustic interferometer to investigate the absorption of ultrasound in liquids is discussed. Following elementary treatments of the propagation of acoustic waves in liquids and the properties of the piezoelectric sound source, a simple method is developed for measuring the sound absorption coefficient. Emphasis throughout the paper is placed on the concepts of the acoustic impedance of the liquid and the effective electrical impedance of the sound source.
A Universal Microwave Probe
Authors: Comley Robert E. , Talham Robert J.
Published: August 2005

A probe of electromagnetic waves has been developed and employed for classroom demonstrations of both standing electric waves and standing magnetic waves. By a “twist of the wrist” it was oriented to demonstrate the two waves independently. The field patterns were not appreciably altered by the probe since its dimensions were less than one-tenth wavelength.
Probability and Determinism
Authors: Yevick Miriam Lipschutz
Published: August 2005

Various physical examples are displayed in which the probability distribution can be traced back to its causal origin. It is argued that probability is never irreducible, but is, in principle, always derivable from a deterministic process which determines its numerical value. It is suggested that deterministic and probabilistic theories are interlocked, each presenting a different aspect of reality, yet that no description of the laws of nature in terms of either of these concepts will ever be ultimate.
Theory for Simple Machines
Authors: Jensen Harald C.
Published: August 2005

A theory is presented for a simple machine that gives a relationship between the efficiency and the load lifted by the machine. The theory is shown to be valid for data taken from a pulley system.
Notes on Jumping
Authors: Kirkpatrick Paul
Published: August 2005

Sutton's conclusion about the forces on the human tibia is shown to be invalid but correct. There is no rational basis for the fairly common impression that broad jumpers should take off at 45°. Subject to simplifying assumptions about the mechanism of the broad jumper it is shown that athletes in this event should take off at less than full speed. The leg motions of broad jumpers in air serve a useful purpose. The application of physics and other sciences to the techniques of sport is a neglected but promising enterprise.
Determination of the Velocity of Light from Electromagnetic Measurements According to W. Weber and R. Kohlrausch
Authors: Kirchner F.
Published: August 2005

In 1856 a paper by W. Weber and R. Kohlrausch was published in Poggendorf's Annalen (Vol. 99, p. 10) under the title: “The Quantity of Electricity which flows in Galvanic Currents through the Cross-Section of a Conductor.” This paper represents a short abstract of a detailed paper by the same authors which appeared in the same year 1856 in the Abhandlungen der Koeniglich Saechsischen Gesellschaft der Wissenschaften, in Leipzig as “Electrodynamic Measurements Particularly Basing Current Intensity Measurements on Mechanical Measurements.” The results of these measurements, which the two authors report in these papers, became of such fundamental importance for the further development of physics that a commemoration of this pioneering work, which in the last decades has been given little attention, seems desirable.
David Alter on the Light of the Electric Spark
Authors: Watson E. C.
Published: August 2005

The one hundred and fiftieth anniversary of the birth of the American physician and physicist, David Alter, occurs this year. It is proposed to celebrate this anniversary by reproducing his two pioneer papers in spectrum analysis published in 1854 and 1855 in the American Journal of Science.
Pinhole-Camera Experiment for the Introductory Physics Course
Authors: Baez Albert V.
Published: August 2005

The pinhole-camera experiment serves as an introduction to geometrical and physical optics as well as the theory and practice of photographic processing. Factors affecting exposure, density, and resolution may be studied experimentally with this inexpensive piece of equipment.
Demonstration of Gravitational Attraction with the Cavendish Balance
Authors: Meissner Hans
Published: August 2005

A Cavendish balance is described, which has a period of 3.5 min and gives a deflection of the light beam of 3 mm at a distance of 1 m when the position of the outer spheres is changed. This deflection is read with a pair of phototubes which, driving a cathode follower, give a current of 44 µa or more depending on the tube used for the cathode follower. The current can be read with a projection meter. The damping of the balance can be adjusted between critical damping and almost zero.
Two-Nucleon Forces and Nuclear Saturation
Authors: Karplus Robert , Watson Kenneth M.
Published: August 2005

Brueckner has adduced considerable evidence that the observed proton-proton, proton-neutron, and neutron-neutron forces lead to stable atomic nuclei whose density is independent of their size. The experimental information and the theoretical arguments that lead to this conclusion are reviewed.
Optimum Pay-Load-Ratio Relation for Multiple-Stage Rockets
Authors: Leitmann G.
Published: August 2005

The principle of the multiple-stage rocket is reviewed. It is shown that the burn-out velocity of a multiple-stage rocket is higher than that of a single-stage rocket of the same over-all mass ratio. It is also shown that the over-all pay-load ratio of a multiple-stage rocket required to reach a given velocity is minimum when the pay-load ratios of all stages are equal. Departure from this equality is demonstrated to have little effect on the over-all pay-load ratio.
Evaluating Laboratory Instruction by Use of Objective-Type Tests
Authors: Kruglak Haym
Published: August 2005

More reliable techniques are needed for evaluating laboratory instruction in general physics. The advantages and disadvantages of objective-type tests are presented. The applications of multiple-choice items in the laboratory are discussed. There is need for research on evaluating laboratory instruction.
On the Classical Laws of Motion
Authors: Eisenbud Leonard
Published: August 2005

A number of logical objections may be raised against the classical laws of motion as they are formulated by Newton and as they are usually presented in textbooks of physics. These objections, which center about the conceptions of mass and force, were first clearly presented by Mach and Poincaré among others. Although these objections are widely known, there appear to be few attempts to present the classical laws in a logically unobjectionable manner and in such a way as to bring out the essential significance of the force and mass concepts. It is the purpose of the following paper to suggest a reformulation of the basic laws of motion. After a short introduction (Sec. 1) the objections to Newton's presentation of the laws of motion are reviewed (Sec. 2). In Sec. 3, the classical laws are given a new formulation.
On the Teaching of “Standing Waves”
Authors: Rekveld J.
Published: August 2005

In introductory physics courses “standing waves” are generally explained as the result of an interference between two progressive waves traveling in opposite directions. A theoretical discussion of the fundamental differential equation for motions of this sort leads to an alternative approach in which these motions are considered as natural modes of vibrations (eigen-vibrations). An outline for a teaching method emphasizing this aspect is given.
Vacuum Electrodynamics on a Merry-Go-Round
Authors: Ise John , Uretsky Jack L.
Published: August 2005

Maxwell's equations in a relativistic, rotating reference frame are discussed by use of a covariant formalism.
Elliptic Orbits in a Frictional Atmosphere
Authors: Parkyn D. G.
Published: August 2005

The instantaneous effect of friction on an elliptic orbit is commonplace mechanics, but the long-term effect of an atmosphere of variable density introduces some features of interest. In this paper an “atmosphere” is postulated which is in agreement with the rather sparse data available and the consequences for elliptic orbits are investigated. The analysis developed is general but the numerical results deduced are of course dependent upon the available data, with the consequent possibility of error. The problem of the life span of a satellite is solved, the numerical values taken being those for Sputnik I.