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Jan 2001

Volume 69, Issue 1, pp. 10-95

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American Association of Physics Teachers 2000 Oersted Medalist: John G. King

Thomas L. O’Kuma

American Journal of Physics -- January 2001 -- Volume 69, Issue 1, pp. 10 | Cited 2 times

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01.10.Cr Announcements, news, and awards

“Observation, Experiment, and the Future of Physics” John G. King’s acceptance speech for the 2000 Oersted Medal presented by the American Association of Physics Teachers, 18 January 2000

John G. King

American Journal of Physics -- January 2001 -- Volume 69, Issue 1, pp. 11

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Looking at our built world, most physicists see order where many others see magic. This view of order should be available to all, and physics would flourish better in an appreciative society. Despite the remarkable developments in the teaching of physics in the last half century, too many people, whether they’ve had physics courses or not, don’t have an inkling of the power and value of our subject, whose importance ranges from the practical to the psychological. We need to supplement people’s experiences in ways that are applicable to different groups, from physics majors to people without formal education. I will describe and explain an ambitious program to stimulate scientific, engineering, and technological interest and understanding through direct observation of a wide range of phenomena and experimentation with them. For the very young: toys, playgrounds, kits, projects. For older students: indoor showcases, projects, and courses taught in intensive form. For all ages: more instructive everyday surroundings with outdoor showcases and large demonstrations. © 2001 American Association of Physics Teachers.
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01.55.+b General physics
01.75.+m Science and society
01.40.-d Education
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The nature of discovery in physics

Douglas D. Osheroff

American Journal of Physics -- January 2001 -- Volume 69, Issue 1, pp. 26

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By their very nature, those discoveries which most change the way we perceive our physical universe are difficult to anticipate. How then, are such discoveries made, and what experimental approaches are most likely to lead to discoveries? In this article I will describe four experiments in which I have participated that have yielded unexpected new physics, and attempt to explain how they came about. © 2001 American Association of Physics Teachers.
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01.55.+b General physics
01.50.-i Educational aids

A closer look at tumbling toast

M. E. Bacon, George Heald, and Matt James

American Journal of Physics -- January 2001 -- Volume 69, Issue 1, pp. 38 | Cited 3 times

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The study of the mechanics of tumbling toast provides an informative and entertaining project for undergraduates. The relatively recent introduction of software packages to facilitate the analysis of video recordings, and the numerical solution of complex differential equations, makes such a study an attractive candidate for inclusion in an experimental physics course at the undergraduate level. In the study reported here it is found that the experimentally determined free fall angular velocity of a board, tumbling off the edge of a table, can only be predicted at all accurately if slipping is taken into account. The size and shape of the board used in the calculations and in the experiments were roughly the same as that of a piece of toast. In addition, it is found that the board, tumbling from a standard table of height 76 cm, will land butter-side down (neglecting any bounce) for two ranges of overhang (δ0). δ0 is defined as the initial distance from the table edge to a vertical line drawn through the center of mass when the board is horizontal. For our board (length 10.2 cm) the approximate ranges of overhang are 0–0.8 and 2.7–5.1 cm. The importance of the 0–0.8 cm (only 2% of all possible overhangs for which tumbling is possible) favoring a butter-side down landing should not be underestimated when pondering the widely held belief that toast, tumbling from a table, usually falls butter-side down. © 2001 American Association of Physics Teachers.
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01.50.-i Educational aids
01.50.ht Instructional computer use
45.05.+x General theory of classical mechanics of discrete systems
45.10.-b Computational methods in classical mechanics
02.60.Lj Ordinary and partial differential equations; boundary value problems

Classical illustrations of CP violation in kaon decays

Jonathan L. Rosner and Scott A. Slezak

American Journal of Physics -- January 2001 -- Volume 69, Issue 1, pp. 44 | Cited 5 times

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It is easy to construct classical two-state systems illustrating the behavior of the short-lived and long-lived neutral K mesons in the limit of CP conservation. The emulation of CP violation is more tricky, but is provided by the two-dimensional motion of a Foucault pendulum. Analogies are drawn between the pendulum and observables in neutral kaon decays. An emulation of CP and CPT violation using electric circuits is also discussed. © 2001 American Association of Physics Teachers.
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01.50.-i Educational aids
13.20.Eb Decays of K mesons
13.25.Es Decays of K mesons
14.40.Be Light mesons (S=C=B=0)
11.30.Er Charge conjugation, parity, time reversal, and other discrete symmetries
45.30.+s General linear dynamical systems

“Franklin’s Bells” and charge transport as an undergraduate lab

R. V. Krotkov, M. T. Tuominen, and M. L. Breuer

American Journal of Physics -- January 2001 -- Volume 69, Issue 1, pp. 50 | Cited 2 times

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“Franklin’s Bells” is a popular lecture demonstration in electricity but seems to have been overlooked as a quantitative undergraduate lab experiment. In our version, a charged ball oscillates back and forth between the plates of a capacitor. This paper has two purposes: one is to discuss some of the wide variety of experiments and calculations which this system affords, the other is to present an analysis of a particular situation in which the ball excites resonant modes of the plates. This excitation gives rise to unexpected steps in the graph of shuttle frequency versus the potential difference between the plates. The apparatus required to show the demonstration is available in most physics departments. Similarly, a quantitative experiment for an introductory undergraduate lab does not require any unusual equipment, nor particularly high voltages. (In our experiment, the highest voltage used was 600 V; this can probably be reduced by scaling down the apparatus.) The physical situation may be analyzed at many different levels, suitable for students in the freshman to senior years, and ranging from a qualitative understanding of the demonstration to computer calculations of chaotic dynamics. The apparatus may be a simple one appropriate to the introductory level, or, at an “Advanced Lab” level, a sophisticated one, with computer-controlled measurements and analysis of various parameters. It is surprising that such a rich system has been neglected in the traditional curriculum. © 2001 American Association of Physics Teachers.
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01.50.Pa Laboratory experiments and apparatus
41.20.-q Applied classical electromagnetism

Quantum revivals versus classical periodicity in the infinite square well

Daniel F. Styer

American Journal of Physics -- January 2001 -- Volume 69, Issue 1, pp. 56 | Cited 24 times

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A particle of mass M moves in an infinite square well of width L (the “particle in a box”). Classically, the motion has period Lmath, which depends on the initial condition through the energy E. Quantum mechanically, any wave function repeats exactly with period 4ML2/πℏ, independent of the initial condition. Given this qualitative difference, how can the classical motion possibly be the limit of the quantal time development? The resolution of this paradox involves the difference between the exact revival (recurrence) of the wave function and the approximate periodicity of expectation values such as 〈x(t)〉. (The latter may recur an odd integral number of times before the full wave function recurs.) The period of the expectation values does depend on the initial condition and can possess the expected classical limit. [An Appendix demonstrates that, under suitably quasiclassical conditions, the quantal time evolution of 〈x(t)〉 passes over to the classical result not only in period, but also in its exact functional form. Another Appendix proves four theorems concerning state-dependent exact revival times.] © 2001 American Association of Physics Teachers.
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01.50.-i Educational aids
03.65.Sq Semiclassical theories and applications

Relative motion of orbiting bodies

Eugene I. Butikov

American Journal of Physics -- January 2001 -- Volume 69, Issue 1, pp. 63 | Cited 2 times

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A problem of relative motion of orbiting bodies is investigated on the example of the free motion of any body ejected from the orbital station that stays in a circular orbit around the earth. An elementary approach is illustrated by a simulation computer program and supported by a mathematical treatment based on approximate differential equations of the relative orbital motion. © 2001 American Association of Physics Teachers.
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01.50.-i Educational aids
45.50.Pk Celestial mechanics
95.10.Ce Celestial mechanics (including n-body problems)

How to teach statistical thermal physics in an introductory physics course

Koo-Chul Lee

American Journal of Physics -- January 2001 -- Volume 69, Issue 1, pp. 68 | Cited 3 times

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We report on several simulation programs (available through http://phys.snu.ac.kr/howto/ or http://phya.snu.ac.kr/∼kclee/howto/) which can be used to teach the statistical foundations of thermal physics in introductory college physics courses. These programs are simple applications of a technique for generating random configurations of many dice with a fixed total value. By merely simulating dice throwing we can demonstrate all the important principles of classical thermodynamics. © 2001 American Association of Physics Teachers.
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01.50.-i Educational aids
05.20.-y Classical statistical mechanics
05.70.-a Thermodynamics

Enhancing electromagnetism experiments with clamp-on ammeters

Dennis C. Henry

American Journal of Physics -- January 2001 -- Volume 69, Issue 1, pp. 76

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Experiments designed to illustrate the principles embodied in Ampere’s Law and Faraday’s Law often depend on the knowledge of the number of turns of wire on various types of laboratory coils. The lack of direct measurement of this parameter can be overcome with the use of inexpensive (<$85) digital clamp-on ammeters. The meters themselves illustrate the connection between the current enclosed by a closed path and the line integral of the magnetic intensity H around that contour. In this paper we present laboratory exercises that make essential use of clamp-on ammeters. © 2001 American Association of Physics Teachers.
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01.50.My Demonstration experiments and apparatus
41.20.-q Applied classical electromagnetism

An introduction to Pound–Drever–Hall laser frequency stabilization

Eric D. Black

American Journal of Physics -- January 2001 -- Volume 69, Issue 1, pp. 79 | Cited 133 times

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This paper is an introduction to an elegant and powerful technique in modern optics: Pound–Drever–Hall laser frequency stabilization. This introduction is primarily meant to be conceptual, but it includes enough quantitative detail to allow the reader to immediately design a real setup, suitable for research or industrial application. The intended audience is both the researcher learning the technique for the first time and the teacher who wants to cover modern laser locking in an upper-level physics or electrical engineering course. © 2001 American Association of Physics Teachers.
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01.50.-i Educational aids
42.60.Da Resonators, cavities, amplifiers, arrays, and rings
42.60.Fc Modulation, tuning, and mode locking
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Walking a charged pith ball perpendicular to an electric field

P. J. Ouseph and C. L. Davis

American Journal of Physics -- January 2001 -- Volume 69, Issue 1, pp. 88

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The net motion of a charged particle in the electric field between two plates of an almost parallel plate capacitor is in a direction perpendicular to the electric field. An apparatus to demonstrate this effect is discussed and the motion of the charged particle is described by simple theoretical considerations. © 2001 American Association of Physics Teachers.
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01.50.-i Educational aids
41.20.Cv Electrostatics; Poisson and Laplace equations, boundary-value problems

An optical technique for studying phase transitions

Carlos Hunte, Peter Gibbs, and Upindranath Singh

American Journal of Physics -- January 2001 -- Volume 69, Issue 1, pp. 91 | Cited 2 times

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Abstract Unavailable
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01.50.Pa Laboratory experiments and apparatus
61.30.Eb Experimental determinations of smectic, nematic, cholesteric, and other structures
64.70.M- Transitions in liquid crystals
78.20.Ek Optical activity
42.70.Df Liquid crystals
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Quintessence: The Mystery of Missing Mass in the Universe

Lawrence Krauss, Author and Virginia Trimble, Reviewer

American Journal of Physics -- January 2001 -- Volume 69, Issue 1, pp. 93

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Abstract Unavailable
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01.30.Vv Book reviews
98.80.-k Cosmology

Quantum Philosophy: Understanding and Interpreting Contemporary Science

Roland Omnès, Author and Daniel Greenberger, Reviewer

American Journal of Physics -- January 2001 -- Volume 69, Issue 1, pp. 94

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Abstract Unavailable
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01.30.Vv Book reviews
03.65.-w Quantum mechanics
01.70.+w Philosophy of science
98.80.-k Cosmology
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