bluuebunny/crossref_metadata_2025 huggingface dataset:
A Correction to the Treatment of Fresnel Diffraction
Authors: Andrews C. L.
Published: August 2005

Measurements of the diffraction pattern of microwaves near circular apertures reveal the quantitative correctness of Kirchhoff's obliquity factor. It has been customary in textbooks of physical optics to assume with Fresnel that the amplitude from zones an infinite distance from the center of the aperture is zero. However, according to Kirchhoff's equation, the amplitude from a zone as the zone number increases without bound is not zero but half the amplitude from the central zone. It is noted that a marginal correction in the textbooks will give results that agree not only with the observed behavior of light, but of microwave diffraction as well, up to the plane of the aperture. The more daring instructor may wish to make a more complete break with the past and explain the diffraction pattern on the basis of Thomas Young's theory. By Young's simple theory that the diffraction pattern of the aperture is an interference pattern between the incident wave and secondary waves from the edge of the aperture, the positions of maximum and minimum intensity may be predicted not only in the Fresnel region but also behind the aperture and in the plane of the aperture itself.
Electric and Magnetic Forces: A Direct Calculation. I
Authors: Brown William Fuller
Published: August 2005

In I, the forces acting on an arbitrary portion of an electrically or magnetically polarized body are calculated without introduction of energy arguments, of an atomic model of the polarization, or of assumptions in regard to the physical significance of the macroscopic field vectors within polarized matter. It is pointed out that a magneto-mechanical formula derived by use of ampèrian currents and one derived by use of magnetic poles will, in general, require different “stress” systems in a given physical situation, because a part of the force that is included in the long-range force in one calculation is attributed to stresses in the other. In the present treatment, dipole-dipole interactions are taken as fundamental; poles and ampèrian currents are regarded as purely formal devices; and the two are treated on an equal footing, so that two equivalent sets of formulas are obtained. In II, the general formulas of I are specialized to the case of a fluid. Formulas relating to electrostriction and to the effect of immersing a body in a fluid are derived; their relation to the traditional formulas (based on energy arguments) is discussed.
Newtonian Mechanics and the Equivalence of Gravitational and Inertial Mass
Authors: Pockman Leonard T.
Published: August 2005

By a historical analysis of the work of Newton and some of his critics and by showing how the equivalence of gravitational and inertial mass can be established in an elementary experimental fashion, it is shown that the presentation of newtonian mechanics can be clarified by emphasizing this equivalence and using it as the starting point.
An Elementary Laboratory in Modern Physics
Authors: Straley Joseph W. , Fussler Karl H. , Shearin Paul E.
Published: August 2005

An introductory course in modern physics for freshmen has been taught at the University of North Carolina for the past three years. The laboratory work consists of a two-hour period each week. Eleven simple experiments have been prepared which illustrate the more significant phases of the subject. Most of the apparatus was constructed in our own shop. The subject matter illustrated by these experiments includes a study of ionization potentials, cathode rays, design and use of a spectroscope, the spectra of atoms and molecules, the photoelectric effect, cosmic rays, and radioactivity.
Magnetically Maintained Pendulum
Authors: Knauss Harold P. , Zilsel Paul R.
Published: August 2005

An iron bob swinging as a pendulum along the axis of a coil toward and away from its center is maintained in motion by feeding alternating current from a low resistance source into the coil which forms part of a suitably tuned circuit. The iron bob may be replaced by a second coil connected in series. The transfer of energy to the pendulum is shown to be due to the phase difference between the variation in the inductance of the circuit and the corresponding variation in the amplitude of the current with the oscillation of the pendulum: if the variation in the current amplitude lags behind the variation in inductance, the pendulum is driven, otherwise it is damped. In the limit of small amplitude of oscillation the condition for maintenance is that the circuit have predominantly inductive reactance and sufficiently high Q.
A Unified Approach to Physics
Authors: Little Noel C.
Published: August 2005

The general elementary course is unified on a basis of underlying theory. Part I introduces seriatim five fundamental concepts to serve a dimensional analysis for the whole of physics. Selected topics make the nature of these concepts clear, e.g., (1) geometric optics for length, (2) kinematics for time, (3) statics of a rigid body for force, (4) electrolysis for electricity, and (5) thermometry and calorimetry for temperature. Part II contains five sections which cut horizontally across the conventional subdivisions of physics. (1) Energetics, in which dynamics, thermodynamics, and the relativity mass-energy relation find a place; (2) Flow Phenomena stress the parallelisms between fluids, heat, and electricity; (3) Field Phenomena apply the inverse square law to gravitation, electro- and magnetostatics, photometry, and radiation; (4) Periodic Phenomena, starting with circular and simple harmonic motions, end with waves of all kinds; and (5) Quantum Phenomena deal with the elemental particles and the indeterminancy principle.
Studies of Transmission Zone Plates
Authors: Myers Ora E.
Published: August 2005

Methods of construction of transmission zone plates are considered. The use of the zone plate for focusing transmitted wavelengths ranging from the infrared to the very soft x-ray region is discussed. An investigation is made of the focal and chromatic properties of a zone plate to be used for visible and near ultraviolet light. Photographs of several lines of the mercury spectrum made by using a zone plate as the focusing “lens” are exhibited. The similarity between the optical properties of a transmission zone plate and a converging lens are shown by both theoretical considerations and experiment.
Demonstration of Phase Shift Using Voltmeters
Authors: Miller Franklin
Published: August 2005

Demonstration of phase shift, attenuated waves, and some properties of oscillators is made with the aid of direct current voltmeters connected to various points in a one-tube phase shift oscillator circuit. Values of circuit components are given for a simple, stable oscillator with a period of the order of 10 to 15 seconds.
The Semidiurnal Tidal Oscillation of the Earth's Atmosphere
Authors: Stolov Harold L.
Published: August 2005

The semidiurnal barometric oscillation, with maxima at about 10 A.M. and 10 P.M. local solar time, is interpreted according to current theory as an air-tide. Although the lunar tidal force is 2.2 times more powerful than the solar, and hence lunar tides in the oceans are 2.2 times stronger than the solar, this is not found to be the case in the atmosphere. The observations show a solar semidiurnal atmospheric oscillation about 100 times greater than might be expected, and a very feeble lunar oscillation. The difficulty is resolved with a suggestion by Kelvin. This is the famous “resonance theory,” and illustrates how the effect of a comparatively small tide-generating force might be magnified, if the atmosphere had a period of free oscillation close to 12 solar hours. The linearized equations of atmospheric oscillations are stated, tidal wind fields indicated, and conclusions summarized.
An Automatic Chart Plotter for Lecture Room Demonstrations
Authors: Nier Alfred O. , Thorness R. B.
Published: August 2005

A recording millivoltmeter is described which gives a record sufficiently large and distinct so that it can be seen by a large lecture audience. The device is useful for showing lecture room demonstrations in which currents or voltages vary with time and the audience needs a record to help appreciate the significance of the experiment. By means of connections to research apparatus in another part of the building, one may often perform actual experiments in front of a large class.
The Harvard Case Histories in Experimental Science: The Evolution of an Idea
Authors: Shirley John W.
Published: August 2005

This is a discussion of the fundamental ideas behind the Case Histories prepared under the direction of President Conant for use in a general education course, Natural Science 4, at Harvard University. A limitation upon the results achieved in this program by lack of integration with other fields is pointed out. Integration of natural science with the humanities, social sciences, and biological sciences is established as a goal for general education. Lack of maturity among college students defeats in many cases the attainment of the goal, making necessary a whole-hearted effort to have the interrelations of the various fields constantly stressed in all.
C. V. Boys' Rainbow Cup and Experiments with Thin Films
Authors: Satterly John
Published: August 2005

The paper describes experiments on thin films that can be done easily with Boys' rainbow cup, mounted on a phonic wheel to insure constancy of rotational speed. Although the air within the cup, on one side of the film, has free access to the atmosphere on the other side of the film, the film itself is spherical. A quantitative explanation of the effect is given in terms of Bernoulli's principle.
Binary Numeration before Leibniz
Authors: Shirley John W.
Published: August 2005

Though it is frequently stated that binary numeration was first formally proposed by Leibniz as an illustration of his dualistic philosophy, the mathematical papers of Thomas Hariot (1560–1621) show clearly that Hariot not only experimented with number systems, but also understood clearly the theory and practice of binary numeration nearly a century before Leibniz's time.
The Forms of Cartesian Ovals in an Optical Range
Authors: Farwell H. W.
Published: August 2005

This paper supplements an earlier discussion of Cartesian ovals. Assuming for the first medium a refractive index 1.00, and for the second 1.50 (and vice versa), the forms of these ovals for refraction have been studied for numerous cases. Each curve represents the form for a specified value of k, the ratio of image distance to object distance. The values of k run from +∞ to −∞.
On Aerophysics Research
Authors: Seeger R. J.
Published: August 2005

This paper deals with the scope of the borderline field between aerodynamics and physics, which has become known as aerophysics. It emphasizes the desirability of utilization of ballistics ranges for aerophysics investigation. In this connection, it reviews in outline form the history of ballistics: the age of speculative ballistics, the age of geometrical ballistics, the age of physical ballistics. Examples of aerophysical research are cited from aeroballistics (high speed gas flows) investigations conducted at the Naval Ordnance Laboratory, White Oak, Maryland.
Are X-Ray Tube Demonstrations Safe?
Authors: Schlegel R. , Lee J. C.
Published: August 2005

Measurements of the radiation in the neighborhood of an unshielded demonstration x-ray tube give intensities ranging from 6 roentgens per minute within a few cm of the tube to no appreciable radiation per minute a few meters from the tube. The genetic and body effects of radiation are discussed. These effects are such that x-ray demonstrations should be given with greater care than is perhaps now generally exercised.
The Moment of Inertia and the Period of the Rocking of an Elliptic Band
Authors: Satterly John
Published: August 2005

The radius of gyration of a thin, elliptical band of uniform line density is given (i) by direct evaluation, (ii) from the point of view that the band represents the interval between adjacent ellipses of semiaxes a and b, and (iii) by taking the band between two confocal ellipses. Values of the radii of gyration for several elliptic bands are computed from the three points of view. Experiments in which elliptic bands of brass and glass were rocked on glass plates and on suspended knife-edges gave agreement within 5 percent of the computed radii of gyration.
Photometric Teaching Methods Using Photoelectric Cells
Authors: Andrewes U. , Dillon T. J.
Published: August 2005

Construction details of three photometers, designated as black box, integrating, and hoop types, are given. All photometers use photovoltaic cells as the light-measuring devices. Tests made with these photometers upon filament-type lamps and fluorescent discharge tubes establish the mean horizontal candle power and the mean spherical candle power of light sources normally found in the laboratory. Auxilliary experiments are described for determining the range of validity of the inverse square and cosine laws for the light sources. A table lists the luminous flux for several sources, measured by each type of photometer.
The Knotty Masspoint versus the Rigid Tinplate
Authors: Naymik Daniel A.
Published: August 2005

There is an experiment in sophomore physics called “The Force Board Experiment” or “The Composition and Resolution of Nonparallel, Concurrent Forces.” In the opinion of the author of this article, this experiment does not adequately bridge the gap between the mathematical process of vector addition and the “Study of Forces acting on a Crane,” which is another classical experiment. For this reason the author has originated an experiment which is slightly more difficult than “The Force Board Experiment,” and yet not as difficult as the crane experiment; it is called “The Tinplate Experiment.”
Thermometers of the Royal Society, 1663–1768
Authors: Patterson Louise Diehl
Published: August 2005

Between 1663 and 1665, Robert Hooke designed a thermometer for the Royal Society which served as a standard for the graduation of other seventeenth-century instruments. This paper describes the construction and scale of the standard, the use of Hooke's scale in meteorological diaries of the period 1669 to 1709, and its modification by Francis Hauksbee, the Younger, in the early eighteenth century. It includes a suggestion for interpretation of the barometric observations in Hooke's Guildhall diary. It points out the influence of the Royal Society's meteorological observations in the age of Fahrenheit, Réaumur, and Celsius.
Note on Electromagnetic Moment of Inertia
Authors: Dixon W. R.
Published: August 2005

It is shown that the angular momentum of the stationary electromagnetic field surrounding a classical charged particle may be considered to be localized in the charge distribution. When the magnetic field is considered to be due to rotation of the charge, there exists a moment of inertia tensor relating the angular momentum of the field and the energy of the magnetic field to the angular velocity, just as the angular momentum, kinetic energy of rotation, and angular velocity are related in ordinary mechanics.
The Output Current of a Nonlinear Device
Authors: Salzberg Bernard
Published: August 2005

A voltage consisting of a cosine term superposed on a steady term is applied to the input of a nonlinear device. The output current of the device is zero for negative voltages, and proportional to the nth power of the voltage when it is positive, the exponent n being 1, 32, or 2. The resultant current may be zero, continuous, or discontinuous, depending on the relative values of the steady term and the peak value of the cosine term. In general, the current may be represented by a Fourier series, the coefficients of the various terms of which are functions of n and the magnitudes of the two components of the voltage. For n = 1 and n = 2, these coefficients are expressible in terms of trigonometric functions. For n = 32, the coefficients are given in terms of the complete elliptic integrals K and E. The root-mean-square value of the current, for n = 1, 32, and 2, is given in terms of trigonometric functions. Graphs of coefficients of the leading Fourier terms, and of the root-mean-square current, are presented for both continuous and discontinuous current, for n = 1, 32, and 2.
Physics Cooperates with Civilian Defense
Authors: Karioris Frank G. , Barkow Arthur G.
Published: August 2005

A report on the Radiological Monitoring Course offered as part of the Milwaukee Civilian Defense Program. In the first course 250 firemen, policemen, and people with technical background were trained in the principles of nuclear physics, and the effects, detection, and measurements of radiation. The course consisted of a series of lectures, together with appropriate films on the fundamentals of atomic and nuclear physics. The laboratory sessions consisted in familiarizing the trainees in the handling, reading, and care of three different radiation measuring instruments. Small radium sources were used. The field sessions consisted of the survey of a three curie cobalt-60 source at a local football stadium.
Quantitative Evaluation of Rocket Propellants
Authors: Penner S. S.
Published: August 2005

A method for the quantitative evaluation of chemicals as rocket propellants is described. The procedure utilizes the fact that adiabatic expansion through a nozzle may be considered to be isentropic. Treatments are presented for the two limiting conditions of expansion, corresponding to flow without chemical change and to flow which is characterized, at all times, by the existence of thermodynamic equilibrium.
The Tesla Coil
Authors: Kelley James B. , Dunbar Lee
Published: August 2005

A description of the construction and operation of a replica of a coil, such as Nikola Tesla first described in 1891, is presented.
On a Degeneracy Theorem of Kramers
Authors: Klein Martin J.
Published: August 2005

There is a theorem due to Kramers which states that the energy states of systems with an odd number of electrons remain at least doubly degenerate in the presence of any purely electric fields. The physical significance of this theorem, its proof, and a discussion of the relationship of the Kramers degeneracy and the Wigner time-reversal operation are considered. A proof is given of the theorem that the expectation value of the magnetic moment operator is zero for any nondegenerate state.
The National Science Foundation—Its Organization and Purposes
Authors: Waterman Alan T.
Published: August 2005

The establishment of the National Science Foundation and its anticipated impact on teaching and on basic research in the Natural Sciences are described. Two very important parts of its program are the support of basic research by grants, and the award of fellowships for predoctoral and postdoctoral study.
On the Combination of the Principles of Area-Moment and Superposition
Authors: Simon A. W.
Published: August 2005

The generalized area-moment propositions developed by the author are combined with the principle of superposition to produce an alternative set of generalized area-moment propositions, which are extremely simple and convenient in application. The method is illustrated by treating in detail two standard cases in beam theory. The method can also be applied advantageously to the solution of statically indeterminate beams.
Pressure Energy and Bernoulli's Principle
Authors: Lindsay George A.
Published: August 2005

An effort is made to show that the concept of pressure in an incompressible fluid as energy per unit volume possessed by the fluid is an erroneous one, and that Bernoulli's equation is not to be interpreted as a statement of conservation of energy, but rather as a relation between pressure, velocity, and height in the gravitational field.
The Adsorption of Gases on Metal Filaments, Films, and Single Crystals
Authors: Crowell Albert D.
Published: August 2005

The paper presents the concepts involved in the study of adsorption of gases on solids. Particular stress is placed on the problem of uniform surfaces. An historical study follows which is specifically concerned with (1) metal filaments and evaporated films and (2) surfaces of metal single crystals, both considered as approximations to ideal surfaces for adsorption measurements.
Graduate Study and Research in Physics (Report of the Committee on Facilities for Graduate Study and Research in Physics)
Authors: Brode R. B. , Platt Joseph B. , Watson Bernard B. , Trytten M. H.
Published: August 2005

A survey of staff available, space and library facilities, and research budgets of physics departments in American universities is summarized. Fields of study in institutions offering the Ph.D. and M.S. degrees are itemized.
Experimental Outcomes of Laboratory Instruction in Elementary College Physics
Authors: Kruglak Haym
Published: August 2005

The purpose of the investigation was to compare the learning outcomes of the conventional and the demonstration methods in the general physics laboratory. The achievement criteria were two pencil-paper tests on mechanics theory and laboratory and two laboratory-performance examinations. The analysis of variance and covariance techniques was used to study the effects of the methods, the instructor, and the interactions between methods and instructors. The effects of the following variables were partialled out: scores on the ACE Psychological Examination, scores on a mathematics test, and grades on a pre-test corresponding to each of the four criteria. It was found that the means on one of the performance tests were significantly higher for groups taught by the conventional method. No statistically significant differences in the means traceable to the two methods were found on the other three criteria. No statistically significant differences in the means of the four criteria were traceable to the differences in the four instructors or the interactions between the instructors and methods. The conventional method appeared to be more effective in teaching the simple manipulatory techniques, the understanding of instrumental set-ups, and the skill in solving simple problems using apparatus and materials of the elementary laboratory.
The Fundamental Character of the Photometric System
Authors: Walls Gordon L.
Published: August 2005

It is shown that photometric quantities and units are not psychophysical entities, as officially claimed, since they express no relationships between subjective intensity (brightness) and the true visual stimulus magnitudes (which are energy magnitudes). It is shown that no theoretical barriers exist to the determination of that fraction of one watt at λ555 mμ, which provides one lumen of luminous flux (photometric “light”). It is further shown that this value will equal an absolute number of quanta/sec usefully absorbed in photochemical molecules in the standard observer in a standard state of adaptation, that this number of quanta/sec will be independent of wavelength if the brightness-generating receptors are all alike, and that it will vary with wavelength for purely objective reasons if each color receptor type makes a specific contribution to brightness.

It is concluded that since the lumen is expressible as an absolute number of quanta/sec, there is no intrinsic subjective element in the photometric system and the system is not psychophysical but “100 percent physical.”
Atomic Spectroscopy and Separated Isotopes
Authors: McNally J. R.
Published: August 2005

The advantages in the use of separated isotopes in atomic spectroscopy for the determination of nuclear moments I, μ, Q, and for studies of the isotope-shift phenomena are discussed. Illustrations of spectra are given for mercury, uranium, and samarium. In addition, a summary is given of twenty-two so-called problem nuclei, i.e., those naturally occurring isotopes for which the nuclear moments are completely uncertain. Concluding remarks are made on such problems as the evaluation of the absolute magnitude of isotope shifts, the role of “forbidden transitions” in isotope spectra, and the potential future value of spectro-isotopic assay techniques.
Special Theories of Relativity
Authors: Rosen Nathan
Published: August 2005

For a homogeneous isotropic medium in which some phenomenon takes place with which is associated a limiting speed c′ and which is described by field equations which can be made covariant under linear space-time transformations, it is possible to set up a c′-relativity theory analogous to the Einstein (c-relativity) theory, but with the speed c′ replacing c, the speed of light in empty space. Such a c′-relativity will have a limited domain of validity, but within this domain it can be useful in providing a conceptual framework for the description of phenomena. For different phenomena in different media one can have many different theories of relativity, among which the Einstein theory occupies a distinguished position. Examples of c′-relativity are mentioned, and the one appropriate to the Maxwell equations for a homogeneous isotropic dielectric is discussed.
Some Recent Determinations of the Velocity of Light
Authors: Mulligan Joseph F.
Published: August 2005

A number of important measurements of the velocity of light have been made in recent years. Four of these determinations are here outlined, with emphasis on the experimental techniques used. These include the work of Essen, and of Hansen and Bol, with microwave cavity resonators, Bergstrand's measurements with a modified Kerr-cell technique, and Aslakson's “Shoran” measurements. It is pointed out that these four determinations are consistent among themselves and yield a value very close to 299,790 km/sec for the velocity of light in vacuum. This is completely outside the probable error of the value 299,776±4 km/sec generally accepted by physicists in the years 1934–1949 on the basis of rotating mirror and Kerr-cell measurements. Some possible reasons for this discrepancy are discussed.
Physics Curriculum at Brooklyn College
Authors: Severinghaus Frances O.
Published: August 2005

An evaluation of undergraduate physics training at Brooklyn College has been made and analyzed as an aid to curriculum planning. Physics majors who had been graduated from the college from two to twenty years reported on the general effectiveness of their undergraduate science training and indicated the areas in which the training was lacking.
Modes, Nodes, and Antinodes
Authors: Young Robert W.
Published: August 2005

Student comprehension of certain facts of acoustics is handicapped by conflicting meanings of words used in the teaching of elementary physics. The words partial, overtone, and harmonic are often treated as synonymous with normal mode of vibration. That normal modes are not always harmonic is illustrated by data given for an actual piano string for which the progressive “inharmonicity” is such that the fifteenth mode (for example) has a frequency more than sixteen times that of the first mode. Measurements reported here for the playing of a cornet illustrate that its steady sound is not necessarily (in the sense of the erstwhile synonyms listed previously) a “note compounded of the fundamental and of the partial tones, or overtones, due to the segments.” Vibration antinodes are not always equally spaced in tubular resonators of varying cross section. Elementary textbooks often devote considerable space to the just scale, even though there is almost no experimental evidence that just scales are employed in actual music. On the basis of equal temperament and the standard A of 440 cps agreed upon internationally for musical performance, the frequency of middle C is 261.6 cps and not 256 cps as often cited. Terminology to clarify matters is recommended.
An Undergraduate Course in Radiation Physics
Authors: Zieman Clayton M.
Published: August 2005

A course is described dealing with the basic phenomena of radiation. Knowledge of differential equations is prerequisite. Since no appropriate textbook is available, more than thirty textbooks are mentioned from which a student may draw his material. Laboratory experiments are an important part of the course. Sources of material for these experiments are quoted.
Conductivity Crystal Counters
Authors: Chynoweth A. G.
Published: August 2005

This is a brief review article on conductivity crystal counters in which their main properties and basic principles of operation are described. Their present position in the field of nuclear instrumentation is discussed, it being concluded that there are still many serious problems to be solved before the counters can be of practical use. Some of these problems and the present methods of tackling them are surveyed.
A Solenoidal Spectrometer for the Undergraduate Laboratory
Authors: Wright Byron T.
Published: August 2005

A solenoidal spectrometer is described. This instrument has several features which make it especially adaptable to use in an undergraduate laboratory. One is that the coil geometry is such that the student may readily verify that the range of variation of the magnetic field on the principal axis is less than 14 percent. Secondly, the baffle geometry is of sufficient simplicity to enable the better student to calculate not only the momentum admitted by the baffle system, but as well to predict the line shape for a monoenergetic source, and thus to obtain the theoretical resolution of the instrument. Thirdly, as a result of the first-mentioned features, the instrument is absolute. Construction details are included. For the instrument described, the absolute accuracy is better than 0.4 percent, the resolution is 1.9 percent, and the useful solid angle is 0.8 percent.
Elementary Spinor Theory
Authors: Payne W. T.
Published: August 2005

The basic part of the theory of spinors is developed by elementary means with the use of a simple picture of a spinor and spherical trigonometry. The topics treated are the geometrical description of a spinor, components of a spinor, the equations for the rotation of a spinor, determination of the magnitude function of a spinor, and addition and multiplication of spinors. The relation of spinors to quaternions is briefly discussed. No detailed treatment of the physical applications of spinor theory is given.
Measurement of the Specific Heat at Room Temperature of Copper in the Form of Wire by Electrical Heating
Authors: Ingles A. R.
Published: August 2005

The experiment described has been devised for the purpose of stimulating the interest of advanced students in methods already employed in accredited research; it also offers an exercise in the correction for heat losses by radiation and convection and indicates a method of minimizing conduction loss.

In the original work, the object was to determine the specific heat of nickel at temperatures up to and beyond the Curie temperature; for the purpose of simplification, however, the method has been applied to copper at the temperature of the laboratory.
College Courses in Electron Microscopy
Authors: Weber Robert L.
Published: August 2005

The facilities and plans for instruction in electron microscopy in representative universities are briefly described. Recommendations are presented regarding principal instrumental and specimen techniques to be taught, laboratory equipment, student supplies, and useful publications. These recommendations evolved from an inquiry among those practicing electron microscopy in academic and industrial research laboratories.
An Absolute Ampere Current Balance for Laboratory Use
Authors: Neher H. V.
Published: August 2005

The ampere current balance herein described has been in use for four years as a regular experiment of a sophomore physics course. It has the following merits: (1) It is simple to construct; (2) it is absolute in that the current may be calculated from the dimensions and balancing weight only; (3) it is subject to a high degree of accuracy, especially for the larger currents; (4) it may be used for alternating as well as direct currents; (5) when current is passed through the movable conductor only, the balance may be used to measure the horizontal component of the earth's magnetic field.
Current Status of Nuclear Reactor Theory
Authors: Weinberg Alvin M.
Published: August 2005

The mathematical theory of neutron chain reacting systems bears considerable similarity to the mathematical theory of quantum mechanics since the Schroedinger equation can be viewed as the equation for an infinitely large chain reactor in which the potential function is replaced by the distribution of neutron absorption cross sections. The chain reactor theory, not being self-adjoint, is somewhat more complicated than the Schroedinger equation theory. Nevertheless, perturbation theory, time dependent theory, and the theory of the stationary, i.e., just critical, state can be stated in much the same way as is done in quantum mechanics.
Relationships Between Transport Properties of Gases
Authors: Grilly E. R.
Published: August 2005

Using reliable data on thermal conductivities K, viscosities η, and specific heats cv, values of the important ratio f = K/ηcv have been determined over a wide range of temperature, 80–380°K, for eight gases. For some gases the ratio shows a decrease with increasing temperature and for others an increase. The results and existing theories do not agree on all points. For a monatomic gas, helium, f has a constant value up to 250°K, agreeing with most theories, but it drops at higher temperatures. One diatomic gas, hydrogen, shows a sharp drop, agreeing very well with Eucken's theory. Another diatomic gas, nitric oxide, shows a rise much sharper than predicted by the theory. Other diatomic and polyatomic gases show large deviations from Eucken's theory, mainly in that experimental values rise while the theory predicts a decrease with increasing temperature.
The Concept of Temperature
Authors: Miller A. R.
Published: August 2005

The logical deduction of the existence of the concept of temperature from the laws of thermal equilibrium is examined. The mathematical proof that the relation given by Carathéodory, in his phenomenological discussion of the laws of thermodynamics, is a necessary and sufficient condition is supplied, thus refuting criticism that has been made of his work. The descriptive account sometimes given from a consideration of corresponding isotherms is also examined. It is shown how this qualitative idea can be put into analytical form.
Optical Filters
Authors: Mohler Nora M. , Loofbourow John R.
Published: August 2005

This survey of filters useful in optical work includes the range from ultraviolet through infrared. Descriptions of absorption filters making use of solid, liquid, and gaseous absorbers are treated in Part I. Part II contains descriptions of polarization, interference, and Christiansen types of filter as well as devices occasionally used in lieu of filters such as focal isolation and residual ray apparatus, gratings, and powder films used effectively as scatterers.
The Nuclear Reactor as a Research Implement
Authors: Snell Arthur H.
Published: August 2005

Several of the more significant physical experiments which have been performed in recent years with nuclear reactors as measuring instruments or as neutron sources are described. The examples are selected partly because of their importance and partly with diversification in mind. Short descriptions are given of the pile oscillator method of measuring neutron absorption cross sections, the measurement of neutron capture gamma-ray spectra, the study of neutron resonances by time-of-flight, neutron diffraction, neutron reflection, and the radioactive decay of the neutron.
Experimental Production of a Divergent Chain Reaction
Authors: Fermi Enrico
Published: August 2005

Except for minor editorial revisions this paper is the reproduction of a report written for the Metallurgical Laboratory of the University of Chicago almost ten years ago, after the experimental production of a divergent chain reaction. This report has now been declassified and can be published.

The present first part of the report contains a general description of the first pile and of its operation. The details of the construction, preparation, and testing of the materials and of the instrumentation are given by the members of the groups responsible for the work in Appendices I and II.

The pile had approximately the shape of a flattened ellipsoid of graphite having 388-cm equatorial radius and 309-cm polar radius. The uranium was distributed through the graphite mass in lumps partly of metal and partly of oxide arranged in a cubic lattice array with about 21-cm cell side. The experimental procedure followed in approaching the critical dimensions and in the actual operation of the pile is described. The observed critical dimensions are compared with the expectation from the tests on the various components of the structure.
Reproductions of Prints, Drawings, and Paintings of Interest in the History of Physics. 49. A Sixteenth Century Spectacle Shop
Authors: Watson E. C.
Published: August 2005

This brief note reproduces a charming sixteenth century engraving of a spectacle shop. It is of especial interest to physicists because it shows at a glance how the practical discovery of the telescope and microscope came to be made.
Computation of the Moment of Inertia of Various Bodies by the Approximate Sum of Numerical Series
Authors: Muñiz Eddie Ortiz
Published: August 2005

The paper presents a simple method of computing moments of inertia of various bodies by approximating the sum of numerical series. The method lends itself to be used in a course of college physics where most students are not familiar with calculus.
Determination of Molecular Structure from Microwave Spectroscopic Data
Authors: Kraitchman J.
Published: August 2005

A method is described for determining the position of an atom in a molecule from spectroscopic measurements on two isotopic species of the molecule. The method is applied to various types of molecules; explicit expressions are derived for linear, symmetric top, planar, and nonplanar asymmetric top molecules. The number of isotopic species on which measurements must be made to complete the structural determination, i.e., determine the position of every atom in the molecule, is discussed for various types of molecules. An application of the method to the determination of mass difference ratios is also considered.
Reproductions of Prints, Drawings, and Paintings of Interest in the History of Physics. 50. Fluents and Fluxions
Authors: Watson E. C.
Published: August 2005

The frontispiece of John Colson's The Method of Fluxions and Infinite Series together with explanatory discussion is reproduced. It is an interesting attempt to explain the method of the calculus pictorially.
Two Ballistics Problems of Future Transportation
Authors: Allen William A.
Published: August 2005

Two ballistics problems that may arise in future transportation have been formulated and solved in detail. The first problem is that of a vehicle moving along a great circle of the earth; the second problem is that of a rocket moving radially away from the earth. In both cases the magnitude of the resultant acceleration applied to the body has been set equal to a constant. The value of this acceleration will be determined ultimately by the maximum acceleration that human beings or material objects can withstand.
Demonstrations to Provide Data for Student Computation in Electricity
Authors: Blisard Thomas J. , Greenbaum Bernard A.
Published: August 2005

Two panel boards were devised for use in obtaining data for student computations in electricity, the first for study of Ohm's law and Kirchhoff 's laws applied to networks, and the second for study of line loss in power transmission. The boards are effective teaching aids because of their good visibility and the ease with which circuits can be altered. The data are sufficiently precise to provide for results in agreement with physical laws.
The Uniform Model of the Nucleus
Authors: Weinberg Izabella Goldin , Blatt J. M.
Published: August 2005

The uniform model of the nucleus, proposed by Wigner in 1937, assumes that the motion of the nucleons within the nucleus are so complicated, and the interactions between them are so strong, that the details of the motion are of no great importance. This model, therefore, differs diametrically from the shell model of the nucleus, in which each nucleon is assumed to move independently of all others to a first approximation, the various nucleons filling up a regular sequence of possible orbits (shells). In this paper we re-examine the evidence for the uniform model to see whether, in the light of data accumulated since the time the model was proposed, the agreement between the predictions of the uniform model and experimental binding energies is sufficiently good to serve as an argument against the shell model. This is found not to be the case. The uniform model gives qualitative agreement with experiment, but the detailed quantitative agreement is only moderately good. This rather indifferent record must be compared with the excellent evidence for nuclear shell structure in the same region of mass numbers. Nevertheless, we feel that the uniform model should not be abandoned altogether, but rather should be reinterpreted to apply to the “characteristic state” postulated by Hurwitz and Bethe, rather than to the ground state. No test of this hypothesis is possible until more is known experimentally about the level spectra of nuclei. In this connection a modified semiempirical form is suggested for the density of nuclear levels as a function of excitation energy.
Echo Ranging with Audiofrequencies
Authors: Bradley George
Published: August 2005

The mathematical form of a propagating wave is discussed, and it is pointed out that it may be misleading to emphasize the harmonic form of a wave in the general physics course. A demonstration piece utilizing a sound pulse is described. The demonstration piece is suitable to illustrate (a) the speed of a sound, (b) reflection methods of ranging, and (c) reverberations in rooms.
The Operating Principles of Synchrotron Accelerators
Authors: Blumenthal I. S.
Published: August 2005

The synchrotron accelerator has many varieties. Some confusion exists in the widely scattered literature on particle accelerators as to the basic similarities and differences of the various types. This confusion is partly due to indistinct designation. In this review paper each variety is designated and described as a logical derivation from a previous type, and the basic principle of operation of each is described in turn. Factors governing oscillations in phase and in orbit are listed and described. Basic references are presented covering each point.
Construction of a Diffraction Grating Spectrograph
Authors: Purbrick R. L.
Published: August 2005

The construction and operation of a simple Wadsworth-mounted 21-ft 10-in. diffraction grating spectrograph is described. The instrument covers the range from 9000A to 1800A in the first order with a linear dispersion of 5A/mm.
The Constant Battery Wheatstone Bridge
Authors: Smith T. Townsend
Published: August 2005

The article discusses the sensitivity of a constant battery Wheatstone bridge and shows that under certain conditions the bridge sensitivity will be independent of the magnitude of the resistance to be measured. A chart is given, which indicates for a given resistance the bridge ratio which provides the highest sensitivity.

The bridge is insensitive for measuring resistances which are large in comparison with the resistance of the ratio arms.
Spin Waves in Ferromagnetic and Antiferromagnetic Materials
Authors: Keffer F. , Kaplan H. , Yafet Y.
Published: August 2005

A brief outline is given of the spin-wave approximation to the near ground states of ferromagnetism and antiferromagnetism. Simple pictorial models of spin waves are introduced. These models clarify the striking difference between ferromagnetic spin waves, which obey the dispersion law ω ∝ k2, and antiferromagnetic spin waves, which obey the law ω ∞ k. The proper normal modes for antiferromagnetic spin waves are presented. The nature of ferromagnetic and antiferromagnetic resonance is illuminated from a spin-wave point of view.
Rocking Experiment with Two Degrees of Freedom
Authors: Satterly John
Published: August 2005

A ring stands, with axis horizontal, on a horizontal table and a cylinder is placed, also with axis horizontal, resting within it. If motion in the same horizontal direction be given to both, they both roll and the motion is of no particular interest. If, however, motion in opposite directions be given to the ring and the cylinder “rocking” occurs. This motion is interesting because its theoretical solution involves the use of Lagrangian equations, there being two degrees of freedom. Theory and experiment are here given for rings (thin and thick, complete and semicircular) and cylinders (hollow and solid) of different sizes. Good agreement is observed.
Geometrical Solution for a Nuclear Moment in a Magnetic Field
Authors: Wangsness Roald K.
Published: August 2005

The general solution of the classical equation of motion dμ/dt = g(μ×H), when H consists of a constant field plus a perpendicular rotating component can easily be obtained after transforming the problem to a properly chosen rotating coordinate system. The value of this method for teaching purposes is discussed.
Physics and Physiology in Diving Decompression
Authors: Schenck Hilbert
Published: August 2005

The fundamental problem of not exceeding the critical saturation of nitrogen in a diver's body requires both physics and physiology in its solution. The basic differential equations of nitrogen saturation and desaturation in a specific tissue are integrated over an idealized dive. Constants determined through physiological research can be substituted and a time-depth ascent curve for any tissue established. A stepwise method is outlined whereby critical tissues at each portion of the ascent can fix the proper ascent curve for the entire body. The advantage of pure oxygen breathing is demonstrated numerically and the failure of helium-oxygen mixtures to shorten ascents is explained by use of the derived equations.
A Calculus of Measures and Its Application to the Relation between Rationalized and Unrationalized Electromagnetic Systems
Authors: Barker J. R. , Davies R. O.
Published: August 2005

When changing units and in dimensional analysis it is usual to employ the relation, physical quantity = measure×unit. Neither the “physical quantity” nor the “unit” is supposed to be a real number and yet the formalism is normally effective. This fact is given a rational explanation and the ideas involved are used to discuss certain questions connected with the rationalization of the electromagnetic equations.
Teaching a Philosophy of Experimentation in a Course in Electrical Measurements
Authors: Worrell Francis T.
Published: August 2005

A course in electrical measurements is described wherein the emphasis is shifted from the learning of various electrical measuring techniques to the development of an appreciation of experimental problems in general. This is accomplished by dropping the requirement of written reports, by allowing sufficient time for the performance of each experiment for thoughtful work, and by selecting the experiments for certain features of general experimental significance rather than for specific electrical measuring techniques. Examples are given of typical experiments.
Relativistic Rocket Theory
Authors: Bade W. L.
Published: August 2005

In the relativistic theory of one-dimensional rocket motion in empty space, Ackeret has found the differential equation of motion and the mass-ratio formula. One can obtain a formal solution for the integrated equation of motion X = X(T) in the general case by determining X and T parametrically as functions of the proper time s of the rocket.
Dimensional Theory: Dimensionless Secondary Quantities
Authors: Whyte L. L.
Published: August 2005

In realms where natural constants, l0, t0, or v0, of length, time, and/or velocity, are present, dimensionless secondary quantities can be defined of the form Q′ = f( l0/l, t0/t, v0/v, etc.) are not, in general, expressible as a constant×the product of powers of primary quantities. It is suggested that dimensionless quantities of the form Q′ are required in the theory of interactions.