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Aug 1979

Volume 47, Issue 8, pp. 665-755

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More on ’’Problems’’

V. Srinivasan

American Journal of Physics -- August 1979 -- Volume 47, Issue 8, pp. 665

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Abstract Unavailable
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01.50.-i Educational aids

On ’’Letters to the Editor’’

C. Sharp Cook

American Journal of Physics -- August 1979 -- Volume 47, Issue 8, pp. 665

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Abstract Unavailable
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01.30.-y Physics literature and publications
01.75.+m Science and society

Salt II and food

Thorton Page

American Journal of Physics -- August 1979 -- Volume 47, Issue 8, pp. 665

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01.75.+m Science and society
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Editorial: What is our rationale?

John S. Rigden

American Journal of Physics -- August 1979 -- Volume 47, Issue 8, pp. 667 | Cited 1 time

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Abstract Unavailable
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01.40.G- Curricula and evaluation
01.75.+m Science and society
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American Association of Physics Teachers 1978 Oersted Medalist: Charles Kittel

Robert Karplus

American Journal of Physics -- August 1979 -- Volume 47, Issue 8, pp. 668

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01.10.Cr Announcements, news, and awards
01.60.+q Biographies, tributes, personal notes, and obituaries
64.60.-i General studies of phase transitions
76.40.+b Diamagnetic and cyclotron resonances

Oersted medalist response: Constructive interactions

Charles Kittel

American Journal of Physics -- August 1979 -- Volume 47, Issue 8, pp. 669

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01.10.Cr Announcements, news, and awards
01.60.+q Biographies, tributes, personal notes, and obituaries
64.60.-i General studies of phase transitions
76.40.+b Diamagnetic and cyclotron resonances

American Association of Physics Teachers 1978 Oersted Medalist: Paul E. Klopsteg

Robert Karplus

American Journal of Physics -- August 1979 -- Volume 47, Issue 8, pp. 670

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Abstract Unavailable
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01.10.Cr Announcements, news, and awards
01.60.+q Biographies, tributes, personal notes, and obituaries

Science and society test IV: The 94th Congress

David Hafemeister

American Journal of Physics -- August 1979 -- Volume 47, Issue 8, pp. 671 | Cited 1 time

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Back‐of‐the‐envelope calculations are carried out on some science related issues that surfaced in the 94th Congress (1975–1976) such as: oil pricing, automobile efficiency standards, inter‐racial busing, leverage on uranium exports, enrichment capacities, Project Pacer, and tax incentives for conservation. This approach attempts to find a middle ground in the science and public policy debates between the vague qualitative essays (which often lack substance) and the highly sophisticated quantitative efforts (which only a few understand and/or believe).
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01.75.+m Science and society
89.30.-g Fossil fuels and nuclear power
89.60.-k Environmental studies

Correlation in the Langevin theory of Brownian motion

A. Manoliu and C. Kittel

American Journal of Physics -- August 1979 -- Volume 47, Issue 8, pp. 678

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In Brownian motion the ensemble average of the product of the displacement and the random force is zero. This result was assumed by Langevin to be true, although it appears to contradict the intuitive feeling that the net displacement should be in the direction of the net impulse. The literature contains a statement that the Langevin assumption is incorrect, and this led us to an examination of the question. We show that the relevant correlation function in one dimension is 〈x (t) A (t−τ) 〉=2(kBT/M)[1−exp(−βτ)] which is zero at equal times and approaches 2(kBT/M) as τ→∞.
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05.40.-a Fluctuation phenomena, random processes, noise, and Brownian motion
02.30.-f Function theory, analysis

Holographic animation apparatus

Sean F. Johnston

American Journal of Physics -- August 1979 -- Volume 47, Issue 8, pp. 681

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Simple apparatus for producing strip holograms is described. Moving the object slightly between exposures permits motion to be simulated, analogously to an animated motion picture. The resulting hologram is viewed by scanning the eyes vertically across the slits. The hologram maintains full horizontal parallax, but the slit aperture reduces the vertical viewing angle of the animated object.
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42.40.Kw Holographic interferometry; other holographic techniques
07.68.+m Photography, photographic instruments; xerography
42.40.My Applications
01.50.F- Audio and visual aids

Coulomb phase shift

Charles W. Clark

American Journal of Physics -- August 1979 -- Volume 47, Issue 8, pp. 683

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The relationship between the energy derivative of the Coulomb phase shift and the classical expression for the time delay is discussed.
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03.65.Nk Scattering theory

Astronomical meaning of a tropical year

Reuben Benumof

American Journal of Physics -- August 1979 -- Volume 47, Issue 8, pp. 685

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A tropical year is usually described incorrectly as the actual interval between two successive passages of the Sun through the vernal equinox. These intervals vary from year to year because of the differing periods of the perturbations of the angular velocity of the Earth. A tropical year is correctly defined as the mean interval between two successive passages of the Sun through the mean equinox of date. The time of beginning of spring depends on (i) the perturbations of the angular velocity of the Earth, (ii) the nutation of the Earth’s axis, and (iii) the aberration of light.
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93.30.Vs Tropical regions
92.60.Ry Climatology, climate change and variability
95.10.Ce Celestial mechanics (including n-body problems)

Propagation of a step in the amplitude or envelope of a pulse or wave packet

Henry M. Bradford

American Journal of Physics -- August 1979 -- Volume 47, Issue 8, pp. 688

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The propagation of a steplike change in the amplitude of a dc pulse and a step in the envelope of a plane sinusoidal wave are investigated. It is shown that a step (e.g., the beginning or end of a pulse or wave) propagates like a pulse in the medium; i.e., its velocity is a weighted average of the group velocity, and its rate of spread is determined by the distribution of group velocities within the spectrum of the step. The results apply to a real pulse (e.g., sound) in an infinite, homogeneous, dispersive, lossless medium, and to the quantum‐mechanical wave function of a free particle.
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83.10.Ff Continuum mechanics

Small group approach to introductory physics

William L. Emkey

American Journal of Physics -- August 1979 -- Volume 47, Issue 8, pp. 695 | Cited 1 time

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This paper describes a system which is used to teach introductory physics to students majoring in science and engineering. The class is divided into groups of three and/or four. During class the groups work on their assignments while interacting with both their peers as well as with their instructor. The system was implemented as an alternative to lecture/recitation approach in an attempt to improve the learning environment.
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01.40.G- Curricula and evaluation
01.55.+b General physics

Equivalence of the Maxwell and wave equations

George Patsakos

American Journal of Physics -- August 1979 -- Volume 47, Issue 8, pp. 698 | Cited 1 time

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The conditions under which the inhomogeneous wave equation for the electromagnetic field tensor becomes equivalent to the Maxwell equations are derived for the case of prescribed sources.
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03.50.De Classical electromagnetism, Maxwell equations
41.20.Jb Electromagnetic wave propagation; radiowave propagation

Classical orbits of a charged particle in a magnetic monopole field

R. K. P. Zia

American Journal of Physics -- August 1979 -- Volume 47, Issue 8, pp. 700 | Cited 3 times

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The orbits of a charged particle in the magnetic field due to a magnetic monopole are reexamined and interpreted intuitively: they are straight lines (geodesics) on a cone. The general case in which an arbitrary central force is superimposed is analyzed. It is shown that bound orbits in the central force which do not ordinarily close may be closed by the addition of a monopole of suitable strength.
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45.05.+x General theory of classical mechanics of discrete systems
41.60.-m Radiation by moving charges

Black liquid solar collector demonstrator

F. L. Weichman and D. J. Austen

American Journal of Physics -- August 1979 -- Volume 47, Issue 8, pp. 704

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A solar collector, suitable for an undergraduate laboratory project or lecture demonstration has been built and the details of the construction and the way in which it can be used by students in elementary or advanced courses is described. A simple and efficient system results from using a black liquid to absorb the energy and from using the thermosyphon effect to drive the liquid through the collector. A floodlamp is used as a surrogate sun. The collector is of considerable current interest in the field of solar energy.
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01.50.My Demonstration experiments and apparatus
89.60.-k Environmental studies
84.60.Jt Photoelectric conversion

Modular electronic system for the introductory laboratory

S. Leonard Dart and Eldred F. Tubbs

American Journal of Physics -- August 1979 -- Volume 47, Issue 8, pp. 707

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A system of small inexpensive electronic modules has been developed for instruction in the introductory physics laboratory. These modules may be used to teach digital electronics, construct digital systems for the instrumentation of standard experiments, or, with the addition of standard test equipment, used to teach analog electronics. The modules are described and some of the design considerations given. Typical experiments are described.
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01.50.Pa Laboratory experiments and apparatus
84.30.-r Electronic circuits
85.40.-e Microelectronics: LSI, VLSI, ULSI; integrated circuit fabrication technology

Two‐dimensional appearance of a relativistic cube

F. R. Hickey

American Journal of Physics -- August 1979 -- Volume 47, Issue 8, pp. 711 | Cited 5 times

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The two‐dimensional or ’’photographic’’ appearance of a cube moving at relativistic speeds is investigated. It is shown that the appearance of the cube depends upon whether the camera is held fixed with the optic axis perpendicular to the direction of motion or panned to follow the cube as it moves. The Lorentz contraction, as it is usually defined, is not visible in either case. However, if the camera is rotated, the photographic appearance has some of the characteristics of a picture of a stationary rotated cube.
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03.30.+p Special relativity

Fluorescence spectrum of NaI(Tl) crystal: A laboratory experiment

G. C. Chikkur, M. T. Lagare, and N. Umakantha

American Journal of Physics -- August 1979 -- Volume 47, Issue 8, pp. 715

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A laboratory experiment, using the single‐photon counting technique, to determine the fluorescence spectrum of NaI(Tl) crystal under gamma excitation, is discussed.
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01.50.Pa Laboratory experiments and apparatus
78.55.Fv Solid alkali halides

Cognitive repression in contemporary physics

Evelyn Fox Keller

American Journal of Physics -- August 1979 -- Volume 47, Issue 8, pp. 718 | Cited 2 times

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After more than 50 years of unquestionable success as a theory, questions about the interpretation of quantum mechanics continue to plague both physicists and philosophers. It is argued here that discussions about the meaning of quantum mechanics remain stymied as a result of the failure of physicists to formulate a cognitive paradigm adequate to their theory. The conventional interpretations which they offer can be seen as inadequate in one of two ways — implicitly, they retain one or the other of the two basic tenets of classical physics, the objectivity or the knowability of nature. This, it is argued, can be viewed as a form of cognitive repression of knowledge acquired, but not yet assimilated. A psychological explanation for the persistence of classical beliefs is proposed.
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01.70.+w Philosophy of science
03.65.-w Quantum mechanics

Multipacting mechanism as the origin of breakdown in high‐frequency electrical discharges in gases

G. S. Harmon

American Journal of Physics -- August 1979 -- Volume 47, Issue 8, pp. 722 | Cited 1 time

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The mechanism by which gas at low pressure breaks down when subjected to a high‐frequency electrical field is considerably different from that of other types of electrical discharge. Provided the pressure is sufficiently low, the breakdown electric field strength is independent of the kind of gas, depending instead on the type, condition and separation of electrode surfaces, and the frequency of alternation of the electric field. The multipacting mechanism as developed by several authors is summarized and brought together in a single framework.
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03.50.De Classical electromagnetism, Maxwell equations
51.50.+v Electrical properties (ionization, breakdown, electron and ion mobility, etc.)

Coordinate‐free rotation operator

C. Leubner

American Journal of Physics -- August 1979 -- Volume 47, Issue 8, pp. 727 | Cited 2 times

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The use of a coordinate‐free rotation operator is suggested for the teaching of rotations in Euclidean three space because of its twofold didactic advantage. On the one hand, the only ingredients of the simply structured rotation operator are axis and angle of rotation, in terms of which the student conceives an actual physical rotation. Thus, he is able to write down immediately the correct rotation operator or sequence of rotation operators. Scalar multiplication by the members of a particular set of basis vectors subsequently produces a particular representation in an unambiguous way. On the other hand, the use of the rotation operator as distinct from its various representations stresses the existence of vectors and operators as physical entities independent of an observer’s frame and thus prepares the student at an elementary level for a similar language in modern quantum theory. The potentialities of the coordinate‐free rotation operator approach are illustrated by a number of examples.
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45.05.+x General theory of classical mechanics of discrete systems

Radial flux distribution of low‐energy neutrons

J. Higinbotham

American Journal of Physics -- August 1979 -- Volume 47, Issue 8, pp. 730

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Using a 100 mCi 241Am‐Be neutron source, the radial flux distribution of low‐energy (epithermal) neutrons in distilled water was measured by students in our Advanced Physics Laboratory and the main features of the distribution accounted for on the basis of a simple model.
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01.50.Pa Laboratory experiments and apparatus
28.20.Gd Neutron transport: diffusion and moderation

Doppler shift for a radar echo

R. J. Gleiser

American Journal of Physics -- August 1979 -- Volume 47, Issue 8, pp. 735 | Cited 1 time

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The Doppler shift formula for a radar echo is derived without the use of transformation equations by considering the superposition of the incident and reflected waves. The results are then used as a basis for a discussion of the concepts of proper length and time as regards the transformation properties of wavelength and period in special relativity.
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03.30.+p Special relativity
03.50.De Classical electromagnetism, Maxwell equations
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Determining the energy levels of composite potential wells

M. L. Glasser

American Journal of Physics -- August 1979 -- Volume 47, Issue 8, pp. 738 | Cited 1 time

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Abstract Unavailable
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03.65.Ge Solutions of wave equations: bound states

Domain and range of an operator

Eduardo A. Castro, Franscisco M. Fernández, and Adela Croce

American Journal of Physics -- August 1979 -- Volume 47, Issue 8, pp. 740

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Abstract Unavailable
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03.65.-w Quantum mechanics
02.30.Tb Operator theory

Illustrating the role of principal planes in an optical system

P. L. Dyson

American Journal of Physics -- August 1979 -- Volume 47, Issue 8, pp. 740

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Abstract Unavailable
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01.50.My Demonstration experiments and apparatus
42.79.Bh Lenses, prisms and mirrors

Kepler ellipse

Arjun Tan

American Journal of Physics -- August 1979 -- Volume 47, Issue 8, pp. 741

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Abstract Unavailable
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45.05.+x General theory of classical mechanics of discrete systems
02.40.-k Geometry, differential geometry, and topology
95.10.Ce Celestial mechanics (including n-body problems)

The Bohr‐Einstein ’’weighing of energy’’ debate

W. G. Unruh and G. I. Opat

American Journal of Physics -- August 1979 -- Volume 47, Issue 8, pp. 743 | Cited 7 times

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Abstract Unavailable
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04.20.-q Classical general relativity
01.65.+g History of science

Intuitive understanding of Pauli’s σ matrices

J. S. Levinger and R. M. Lichtenstein

American Journal of Physics -- August 1979 -- Volume 47, Issue 8, pp. 744

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Abstract Unavailable
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03.65.-w Quantum mechanics

One beer for the price of two

Robert B. Prigo, Abel Rosales, Richard B. Harding, and Richard Wormsbecher

American Journal of Physics -- August 1979 -- Volume 47, Issue 8, pp. 744

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Abstract Unavailable
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01.50.My Demonstration experiments and apparatus
42.25.Gy Edge and boundary effects; reflection and refraction
42.66.Si Psychophysics of vision, visual perception; binocular vision

Comments on physics and society at Washington State University

J. Thomas Dickinson

American Journal of Physics -- August 1979 -- Volume 47, Issue 8, pp. 745

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Abstract Unavailable
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01.40.Di Course design and evaluation
01.75.+m Science and society

Rotations, Lorentz transformations, and arbitrary axes

C. B. van Wyk

American Journal of Physics -- August 1979 -- Volume 47, Issue 8, pp. 747 | Cited 2 times

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Abstract Unavailable
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02.40.-k Geometry, differential geometry, and topology

Comment on ’’Maximizing the range of the shot put’’

William Hooper

American Journal of Physics -- August 1979 -- Volume 47, Issue 8, pp. 748

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Abstract Unavailable
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01.50.Pa Laboratory experiments and apparatus
01.55.+b General physics
45.05.+x General theory of classical mechanics of discrete systems

Kinematic strategy of self‐preservation for the jogger

J. D. Memory

American Journal of Physics -- August 1979 -- Volume 47, Issue 8, pp. 749

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Abstract Unavailable
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01.55.+b General physics
01.75.+m Science and society

Erratum: ’’Eddy currents: Levitation, metal detectors, and induction heating’’ [Am. J. Phys. 46, 464 (1978)]

G. Wouch and A. E. Lord, Jr.

American Journal of Physics -- August 1979 -- Volume 47, Issue 8, pp. 750

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Abstract Unavailable
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01.40.G- Curricula and evaluation
41.90.+e Other topics in electromagnetism; electron and ion optics (restricted to new topics in section 41)
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Inexpensive automatic time keeping in the undergraduate laboratory

David Doty

American Journal of Physics -- August 1979 -- Volume 47, Issue 8, pp. 751

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Abstract Unavailable
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01.50.Pa Laboratory experiments and apparatus
06.30.Ft Time and frequency
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Working with Radiation...and Protecting the Unborn (film)

Radiation Management Corporation Producer and Priscilla W. Laws

American Journal of Physics -- August 1979 -- Volume 47, Issue 8, pp. 753

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Abstract Unavailable
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01.50.F- Audio and visual aids
87.55.N- Radiation monitoring, control, and safety
01.75.+m Science and society

The Flight of the Gossamer Condor (film)

Shedd Productions Producer and Daphne Schiff

American Journal of Physics -- August 1979 -- Volume 47, Issue 8, pp. 753

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Abstract Unavailable
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01.50.F- Audio and visual aids
01.65.+g History of science

Simple Harmonic Motion (film)

Pennsylvania State University Producer and Thomas Rossing

American Journal of Physics -- August 1979 -- Volume 47, Issue 8, pp. 754

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Abstract Unavailable
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01.50.F- Audio and visual aids
43.10.Sv Education in acoustics, tutorial papers of interest to acoustics educators
01.55.+b General physics

The Process of Holography (film)

Pennsylvania State University, Producer and Thomas Rossing

American Journal of Physics -- August 1979 -- Volume 47, Issue 8, pp. 754

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Abstract Unavailable
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01.50.F- Audio and visual aids
43.10.Sv Education in acoustics, tutorial papers of interest to acoustics educators
01.55.+b General physics

Sound Fields in Rectangular Enclosures (film)

Pennsylvania State University, Producer and Thomas Rossing

American Journal of Physics -- August 1979 -- Volume 47, Issue 8, pp. 754

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Abstract Unavailable
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01.50.F- Audio and visual aids
43.10.Sv Education in acoustics, tutorial papers of interest to acoustics educators
01.55.+b General physics

A Brief Colloquy on Acoustic Diffraction (film)

Pennsylvania State University, Producer and Thomas Rossing

American Journal of Physics -- August 1979 -- Volume 47, Issue 8, pp. 754

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Abstract Unavailable
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01.50.F- Audio and visual aids
43.10.Sv Education in acoustics, tutorial papers of interest to acoustics educators
01.55.+b General physics

Time Evolution of Coherent States for General Potentials (film)

Vincent P. Gutschick, Producer, Michael Martin Nieto, Producer, Fred Baker, Producer, and Charles A. Nelson

American Journal of Physics -- August 1979 -- Volume 47, Issue 8, pp. 755 | Cited 2 times

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Abstract Unavailable
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01.50.F- Audio and visual aids
03.65.-w Quantum mechanics
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