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Feb 1983

Volume 51, Issue 2, pp. 103-192

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Letter to the Editor

John W. McClain

American Journal of Physics -- February 1983 -- Volume 51, Issue 2, pp. 103

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06.20.F- Units and standards

Letter to the Editor

F. M. Phelps, III

American Journal of Physics -- February 1983 -- Volume 51, Issue 2, pp. 103

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06.20.F- Units and standards

No place for a photon?

H. L. Armstrong

American Journal of Physics -- February 1983 -- Volume 51, Issue 2, pp. 103

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03.65.Ta Foundations of quantum mechanics; measurement theory
14.70.Bh Photons

Letter to the Editor

John M. Fowler

American Journal of Physics -- February 1983 -- Volume 51, Issue 2, pp. 104

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01.40.G- Curricula and evaluation

Poincaré gauge is the multipolar gauge

Donald H. Kobe

American Journal of Physics -- February 1983 -- Volume 51, Issue 2, pp. 105 | Cited 3 times

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11.15.-q Gauge field theories
03.50.Kk Other special classical field theories
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Solutions of January 1983 Problems

Edward M. Purcell, Editor

American Journal of Physics -- February 1983 -- Volume 51, Issue 2, pp. 107

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01.40.-d Education

New Problems

Edward M. Purcell, Editor

American Journal of Physics -- February 1983 -- Volume 51, Issue 2, pp. 107

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01.40.-d Education
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Editorial

Philip B. James, Acting Editor

American Journal of Physics -- February 1983 -- Volume 51, Issue 2, pp. 109

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01.30.-y Physics literature and publications
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The Crane Foucault pendulum: An exercise in action‐angle variable perturbation theory

K. T. Hecht

American Journal of Physics -- February 1983 -- Volume 51, Issue 2, pp. 110

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The short Foucault pendulum recently constructed by H. R. Crane, with a magnetic force field to compensate the intrinsic precession associated with small ellipticity, makes a natural exercise for the classical Poincaré perturbation theory.
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45.05.+x General theory of classical mechanics of discrete systems

An analysis of the rotational stability of the layout back somersault

Paul A. Lightsey

American Journal of Physics -- February 1983 -- Volume 51, Issue 2, pp. 115

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A numerical solution of Euler’s equations for a freely rotating asymmetrical top is applied to an analysis of the relative stability of rotation of a gymnast performing a layout back somersault with and without a full twist. The results suggest that successful performance of the stunt without a full twist has less tolerance for error in the initial rotational velocity than does the stunt with a full twist. This analysis provides an interesting illustration that can be used in advanced undergraduate mechanics courses. The analysis also demonstrates the potential for increased utilization of computers and numerical techniques in the undergraduate curriculum.
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87.19.rs Movement
87.19.ru Locomotion

Transient electric and magnetic fields associated with establishing a finite electrostatic dipole

M. J. Master and M. A. Uman

American Journal of Physics -- February 1983 -- Volume 51, Issue 2, pp. 118 | Cited 10 times

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We obtain analytical solutions in the time domain for the electric and magnetic fields associated with establishing a finite electrostatic dipole. We assume that a simple source current distribution, a square pulse of current, produces the dipole, and solve for the fields produced by that source current distribution using Maxwell’s equations. Salient features of the fields are discussed from a physical point of view. We outline a technique to determine in the time domain the electric and magnetic fields produced by any arbitrary time‐varying current propagating along a straight antenna, given the calculated fields due to a short square pulse of current.
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41.20.Cv Electrostatics; Poisson and Laplace equations, boundary-value problems
41.20.Gz Magnetostatics; magnetic shielding, magnetic induction, boundary-value problems

Death in a hot tub: The physics of heat stroke

Albert A. Bartlett and Thomas J. Braun, M. D.

American Journal of Physics -- February 1983 -- Volume 51, Issue 2, pp. 127

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High environmental temperature and/or vigorous physical work will tend to cause a person’s body temperature to rise. In an attempt to maintain a normal body temperature of 37°C the body then increases its rate of dissipation of heat by mechanisms that involve large increases in the blood flow to the skin. When there is an increase in the fraction of the blood that flows to the skin, the fraction available to other organs will decrease. A decreased flow to the brain can cause unconsciousness or death. The basic elements of this competition can be represented in terms of a simple dc circuit. Here is an example where the elements of dc circuit theory can be coupled with basic concepts of thermodynamics to help demonstrate the complimentarity of different branches of physics and to help students in elementary physics courses to gain an improved understanding of an important physiological situation. Examples of this type seem to be absent from many of our texts for introductory courses in physics.
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87.19.Pp Biothermics and thermal processes in biology

Coherence time in periodically modulated light beams

M. A. Rebolledo and R. J. López

American Journal of Physics -- February 1983 -- Volume 51, Issue 2, pp. 133

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The study of the coherence properties of modulated light sources is interesting since their utilization has increased considerably. After introducing in an intuitive way the coherence time definition, we present a systematic method for calculating the coherence time of a periodically modulated intensity light beam. The results are applied to two cases: chopped light and pulsed laser light. A comment is made about the results and an experiment to prove the change of coherence properties with the modulation period is described.
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42.25.Kb Coherence
42.60.Jf Beam characteristics: profile, intensity, and power; spatial pattern formation

Applying dimensional analysis

Wilfred J. Remillard

American Journal of Physics -- February 1983 -- Volume 51, Issue 2, pp. 137 | Cited 4 times

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The basic concepts of dimensional analysis have been known for over a half century. However, with the advent of hand calculators and the use of matrices these concepts lend themselves to simple manipulations which can assist a researcher in designing experiments, developing equations, and converting units. Matrix methods are developed and examples are given to illustrate these concepts.
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06.20.Dk Measurement and error theory
02.10.Ud Linear algebra
02.10.Xm Multilinear algebra

Green functions and impurities in harmonic chains

D. Prato and C. A. Condat

American Journal of Physics -- February 1983 -- Volume 51, Issue 2, pp. 140 | Cited 1 time

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The density of vibrational states of harmonic chains is calculated with the Green function formalism. Chains with impurities are considered, and it is explicitly shown how the localized states are built up from the contribution of every lattice site to the density of states. The method can be used, with slight changes, to study the dynamics of a linear ferromagnetic lattice with nearest‐neighbor interactions. The procedure employed in this article shows clearly the power and simplicity of the Green function method.
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63.20.Pw Localized modes
75.10.Jm Quantized spin models, including quantum spin frustration

The PET and pendulum: An application of microcomputers to the undergraduate laboratory

Gregory M. Quist

American Journal of Physics -- February 1983 -- Volume 51, Issue 2, pp. 145 | Cited 2 times

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A set of introductory undergraduate experiments designed to illustrate the usefulness of microcomputers for observing and measuring complex physical phenomena is described. A Commodore PET microcomputer is used both as a calculational and data‐collecting tool, investigating the motion of a real pendulum. Students at the introductory level are able to investigate and appreciate some relatively complex dynamics without recourse to advanced mathematics.
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01.50.ht Instructional computer use
01.50.Pa Laboratory experiments and apparatus
45.05.+x General theory of classical mechanics of discrete systems

Experiments with loaded dice

Eugene M. Levin

American Journal of Physics -- February 1983 -- Volume 51, Issue 2, pp. 149 | Cited 1 time

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Plastic cubes (dice) were ‘‘loaded’’ for asymmetric insertion of brass cylinders, thereby displacing the mass center from the geometric center of each cube. The statistics of seven differently ‘‘loaded’’ dice have been studied experimentally, and the results analyzed in terms of a Boltzmann‐like model involving gravitational energy differences among the various orientations. ‘‘Loaded dice’’ may provide interesting and easily visualized systems for the introduction of concepts such as activation energy, degeneracy, partition function, and elementary group theory.
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02.50.Cw Probability theory
05.20.-y Classical statistical mechanics

A real ‘‘thought’’ experiment for the hydrogen atom

I. E. McCarthy and E. Weigold

American Journal of Physics -- February 1983 -- Volume 51, Issue 2, pp. 152 | Cited 2 times

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The absolute square of the normalized position‐space wave function of the electron in a hydrogen atom is interpreted as the probability distribution for observations of the position of the electron. This is only a thought experiment, since the electron’s position cannot be observed. The first observation of the momentum distribution of the electron directly verifies the probability interpretation of the momentum‐space wave function.
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03.65.Ge Solutions of wave equations: bound states
34.80.Dp Atomic excitation and ionization
31.10.+z Theory of electronic structure, electronic transitions, and chemical binding

Near‐resonance absorption processes: A model study

C. K. Au and Y. Aharonov

American Journal of Physics -- February 1983 -- Volume 51, Issue 2, pp. 156 | Cited 1 time

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We construct an exactly soluble model in which an otherwise bound system can make transitions to another channel with a continuous energy spectrum to simulate the decay of an excited atom by the emission of photons. We show that the resonance absorption line shape occurs naturally in such a model.
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03.65.Ge Solutions of wave equations: bound states
32.70.-n Intensities and shapes of atomic spectral lines

A simple, accurate alternative to the minimum deviation method of determining the refractive index of liquids

B. P. Chandra and S. C. Bhaiya

American Journal of Physics -- February 1983 -- Volume 51, Issue 2, pp. 160 | Cited 4 times

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A fixed angle of incidence method, which is an alternative to the minimum deviation method of determining the refractive index of liquid, is used. This method is very simple as compared to others. The value of refractive index determined by this method is nearly the same as that determined by other methods.
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01.50.Pa Laboratory experiments and apparatus
07.60.Hv Refractometers and reflectometers
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)

Elastic vibrations of rods and Poisson’s ratio

Timothy J. Davis and Geoffrey I. Opat

American Journal of Physics -- February 1983 -- Volume 51, Issue 2, pp. 161

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We describe a simple experiment using a stereo phonograph cartridge for observing the longitudinal and torsional vibrations of a cylindrical rod. The elastic properties of the rod may thus be determined from measurements of its natural frequencies. Poisson’s ratio, in particular, is determined to high precision directly from a simple frequency ratio.
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01.50.Pa Laboratory experiments and apparatus
46.40.Cd Mechanical wave propagation (including diffraction, scattering, and dispersion)
46.40.Jj Aeroelasticity and hydroelasticity

Gauge invariance in quantum mechanics: zero electromagnetic field

Donald H. Kobe and Kuo‐Ho Yang

American Journal of Physics -- February 1983 -- Volume 51, Issue 2, pp. 163 | Cited 5 times

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The case of a single charged particle with potential energy is considered when the classical electromagnetic field is zero. The vector and scalar potentials describing this situation are not necessarily zero. When the conventional approach to radiation problems using the interaction A⋅p plus p⋅A plus A2 plus A0 (constants omitted) is used, time‐dependent probabilities are predicted if the vector potential A=−∇Λ≠0 even though the electromagnetic field is zero. The reason for this unphysical behavior is that eigenfunctions of the unperturbed Hamiltonian, which is not gauge invariant, are used to calculate the probability amplitudes. When a manifestly gauge‐invariant procedure is applied to this case the probabilities are constant in all gauges. The reason that physical results are obtained is that eigenstates of the energy operator are used to calculate the probability amplitudes.
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03.65.Ta Foundations of quantum mechanics; measurement theory

Displacement current, transport current, and charge conservation

N. Gauthier

American Journal of Physics -- February 1983 -- Volume 51, Issue 2, pp. 168

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A novel method for introducing Maxwell’s displacement current concept is presented, within the framework of an integral formulation of Maxwell’s equations. The method is general and simple and could be useful to teachers and students of electromagnetism.
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03.50.De Classical electromagnetism, Maxwell equations

Integral equation methods in electrostatics

G. Martínez and M. Sancho

American Journal of Physics -- February 1983 -- Volume 51, Issue 2, pp. 170 | Cited 10 times

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An integral equation approach to the electrostatic problem applied to charged conductors and homogeneous dielectric media is presented for instructional purposes. Several schemes of an approximated solution are obtained by replacing the integral equations with discrete sets of algebraic equations. We study some examples and discuss the advantages of these methods compared with the finite‐difference techniques.
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41.20.Cv Electrostatics; Poisson and Laplace equations, boundary-value problems
41.20.Gz Magnetostatics; magnetic shielding, magnetic induction, boundary-value problems
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Frequency dependence of the skin depth in a metal cylinder

H. D. Wiederick and N. Gauthier

American Journal of Physics -- February 1983 -- Volume 51, Issue 2, pp. 175 | Cited 2 times

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Abstract Unavailable
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01.50.Pa Laboratory experiments and apparatus
73.25.+i Surface conductivity and carrier phenomena

A simple example of a classical gauge transformation

R. C. Whitten

American Journal of Physics -- February 1983 -- Volume 51, Issue 2, pp. 177

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51.10.+y Kinetic and transport theory of gases
11.15.Kc Classical and semiclassical techniques

Kronig–Penney model in reciprocal lattice space

Surjit Singh

American Journal of Physics -- February 1983 -- Volume 51, Issue 2, pp. 179 | Cited 1 time

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Abstract Unavailable
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71.15.-m Methods of electronic structure calculations

The phase

J. Olsen

American Journal of Physics -- February 1983 -- Volume 51, Issue 2, pp. 180

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Abstract Unavailable
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03.30.+p Special relativity

Domino ‘‘chain reaction’’

Lorne A. Whitehead

American Journal of Physics -- February 1983 -- Volume 51, Issue 2, pp. 182

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01.50.My Demonstration experiments and apparatus
01.55.+b General physics

Simple modification of the overhead projector allows vertical formats

Arvid T. Lonseth

American Journal of Physics -- February 1983 -- Volume 51, Issue 2, pp. 183

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Abstract Unavailable
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01.50.My Demonstration experiments and apparatus
01.50.F- Audio and visual aids

A versatile digital timer circuit

David L. DuPuy

American Journal of Physics -- February 1983 -- Volume 51, Issue 2, pp. 183

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06.30.Ft Time and frequency
85.40.-e Microelectronics: LSI, VLSI, ULSI; integrated circuit fabrication technology

Demonstrations for teaching nuclear energy

Joseph Priest and James Poth

American Journal of Physics -- February 1983 -- Volume 51, Issue 2, pp. 185

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01.50.My Demonstration experiments and apparatus
28.90.+i Other topics in nuclear engineering and nuclear power studies (restricted to new topics in section 28)
29.90.+r Other topics in elementary-particle and nuclear physics experimental methods and instrumentation (restricted to new topics in section 29)
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Science in America: A Documentary History 1900–1939

Nathan Reingold, Author, Ida H. Reingold, Author, and R. C. Levine

American Journal of Physics -- February 1983 -- Volume 51, Issue 2, pp. 188

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01.30.Ee Monographs and collections
01.65.+g History of science

Engines, Energy, and Entropy. A Thermodynamics Primer

John B. Fenn, Author and Ralph Baierlein

American Journal of Physics -- February 1983 -- Volume 51, Issue 2, pp. 189

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01.30.mp Textbooks for undergraduates
05.70.-a Thermodynamics

POST‐USE REVIEW: The Art of Electronics

Paul Horowitz, Author, Winfield Hill, Author, and Paul W. Zitzewitz

American Journal of Physics -- February 1983 -- Volume 51, Issue 2, pp. 190

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Abstract Unavailable
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01.30.mp Textbooks for undergraduates
84.30.Bv Circuit theory
84.30.-r Electronic circuits
85.40.-e Microelectronics: LSI, VLSI, ULSI; integrated circuit fabrication technology

POST‐USE REVIEW: An Introduction to Error Analysis: The Study of Uncertainties in Physical Measurements

John R. Taylor, Author, Mark D. Semon, and John K. Pribram

American Journal of Physics -- February 1983 -- Volume 51, Issue 2, pp. 191

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Abstract Unavailable
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01.30.mp Textbooks for undergraduates
06.20.Dk Measurement and error theory
07.05.Hd Data acquisition: hardware and software
07.05.Kf Data analysis: algorithms and implementation; data management
07.05.Rm Data presentation and visualization: algorithms and implementation
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