American Journal of Physics, 1996 February

Am. J. Phys. Vol. 64, No. 2, Feb 1996, Pages 114-119
Millikan Lecture 1995: Do they just sit there? Reflections on helping students learn physics
Dean Zollman

Department of Physics, Kansas State University, 116 Cardwell Hall, Manhattan, Kansas 66506-2601

Am. J. Phys. Vol. 64, No. 2, Feb 1996, Pages 120-135
Resource letter EPA-1: Electronic plymers and their applications
J.W. Blatchford

Dept of Physics, Ohio State University, Comulbus Ohio 43210-1106
A.J. Epstein
Dept of Physics, and The Department of Chemistry, Ohio State University, Comulbus Ohio 43210-1106

Am. J. Phys. Vol. 64, No. 2, Feb 1996, Pages 136-144
Poles, bound states, and resonances illustrated by the square well potential
D.W.L. Sprung and Hua Wu

Department of Physics and Astronomy, McMaster university, Hamilton, Ontario L8S 4M1, Canada
J.Martorell
Dept. d'Estructura i Constituents de la Materia, Facultat Fisica, University of Barcelona, Barcelona, Barcelona 08028, Spain
(Received 25 April 1994; accepted 19 May 1995)
Poles of the S matrix in the complex momentum plane are known to be related to the bound states, virtual states, and transmission resonances of the potential. We illustate this by tracing the motion of the poles in the case of a square well in one dimension. The conditions for appearance of prominant resources are clarified. It is shown that the geographical solution due to Pitkanen provides the virtual or antibound states as well as the bound states. A near-threshold formula for the binding energies is presented that also works for the antibound states.

Am. J. Phys. Vol. 64, No. 2, Feb 1996, Pages 144-146
The physical pendulum on a cylindrical support
David A Giltinan, David L. Wagner, and Thomas A Walkiewicz

Department of Physics and Tecnology, Edinboro University of Pennsylvania, Edinboro, Pennsylvania 16444
(Received 22 December 1995; accepted 13 March 1995)
An alternative derivation is presented for the period of a physical pendulum rotating on a cylindrical support. Absolute and relative accelerations are used to obtain the equations of motion for the pendulum.

Am. J. Phys. Vol. 64, No. 2, Feb 1996, Pages 147-150
Analysis of idealized Zeeman quantum beat experiments in the advanced laboratory
Gregory J. Germmen and N. Rouze

Department of physics, Hope College, Holland, Michigan 49423
(Received 6 June 1994; accepted 16 April 1995)
An expression for the time-dependent intensity of light scattered in idealized Zeeman quantum beat experiments commonly found in advanced teaching laboratories is presented. The development of this expression illustrates the separation of geometrical and dynamic factors via the Wigner-Eckart theorem. The experiment is also interpreted in terms of a pictorial description of a rotating electron cloud, and an experimental procedure ro illustrate this rotation is described.

Am. J. Phys. Vol. 64, No. 2, Feb 1996, Pages 151-156
Random-exchange Ising model with spatially correlated disorder
Erik K. Hobie

Department of Physics and Astronomy, University of wisconsin-River Falls, River Falls, Wisconsin 54022
(Received 14 November 1994; accepted 28 April 1995)
The pair correlation function g(r.r') is derived in the mean-field approximation for a "random-exchange" Ising ferromagnet with long range spatial correlations in the disorder. The static structure factor S(q) describing the intensity of scattered electromagnetic radiation or neutrons is then calculated. The inadequacy of a mean-field treatment is demonstrated, and the physical aspects of renormalization are discussed. From a pedagogical perspective, this problem offers a contemporary application of a number of techniques typically encountered in an advanced undergraduate or first-year graduate course in mathematical physics and can be used at that level to introduce the concept of renormalization.

Am. J. Phys. Vol. 64, No. 2, Feb 1996, Pages 156-163
ON the concept for a Fabry-Perot interferometer
J.J. Monzon and L.L. Sanchez-Soto

Departmento de Optica, Facultad de Ciencias Fisicas, Universidad Complutense, 28040 Madrid, Spain
(Received 28 November 1995; accepted 28 May 1995)
We argue that the Fabry-Perot interferometer should be modeled as a transparent medium between two absorbing coatings of finite thickness. Using the scattering-matrix formalism, we show that the transmittance obeys an Airey function, but not the reflectance, because of absorbtion and the coupling between the multiple reflected waves in the coatings. The model allows us to compute the absorbtance in each coating and to explain a number of previous experimental results. The Stokes relations are generalized for this model.

Am. J. Phys. Vol. 64, No. 2, Feb 1996, Pages 196-169
The hydrolic jump in radially spreading flow: A new model and new experimental data
B.L. Blackford

Department of Physics, Dolhousie University, Halifax, Nova Scotia B3H 3J5, Canada
(Received 8 June 1995; accepted 6 April 1995)
A new model for the hydraulic jump in radially spreading flow is presented. The equation of motion for a liquid annulus spreading out under the influence of hydrostatic pressure gradient and frictional drag is developed. The resulting nonlinear differential equation for the liquid depth, h(r), is solved by computer simulation. The jump is assumed to begin when the laminar flow is engulfed by the underlying boundary layer liquid, as suggested recently in the literature. This complicated mixing process is crudely modeled by a drag term which slows the flow and initiates a positive feedback mechanism culminating at a new critical depth, beyond which the depth increases asymptotically to a final value. The model predicts a new relationship between the laminar flow depth just before the jump and the final depth. An experimental apparatus was built to make detailed measurements of the depth h(r), both in the region before the jump and beyond the jump. The theoretical predictions were compared to the experimental data, and gave surprisingly good agreement by suitable adjustment of the two parameters k and C of the model. The parameter k determines the growth rate of the boundary layer thickness, and C determines the drag force. The results suggest that the usual textbook assumption of zero momentum loss across the jump is not appropriate for this type of hydraulic jump. The case of a hydraulic jump in the absence of gravity is considered also and a much different behavior is predicted, which could be tested by experiment in a microgravity environment.

Am. J. Phys. Vol. 64, No. 2, Feb 1996, Pages 170-173
Resonance response of a moderately driven rigid planar pendulum
Randall D. Peters

Department of Physics and Engineering Physics, Texas Tech University, P,O, Box 41051, Lubbock, Texas 79409-1051
(Received 8 August 1995; accepted 26 April 1995)
The steady-state motion of a rigid planar pendulum has been studied as the drive frequency was tuned through "resonance" of the pendulum. Depending on amplitude of the drive, dramatically different responses were observed. The only motions studied in detail were ones involving period-one limit cycles. A range of surprisingly large hysteresis was discovered, in which amplitude jumps occur in only one direction. A highly nonlinear mode, that is not chaotic, was discovered. It is apparently known by bell ringers but not by physicists. Amplitude jumps out of the bell-ringer mode appear to exhibit transient chaos for some cases.

Am. J. Phys. Vol. 64, No. 2, Feb 1996, Pages 174
Notes and Discussion: An entangled opinion on the interpretation of quantum mechanics
A.C. de la Torre

Department de la Fisica, Universidad National de Mar Plato, Funes 3350, 7600 Mar Del Plata Argentina
A.C. Dotson
Department of Chemistry and Physics, St Andrew Presbyterian College, Laurinburb, North Carolina
(Received 11 January 1995; accepted 3 April 1995)

Am. J. Phys. Vol. 64, No. 2, Feb 1996, Pages 175
Response to "comment on 'Scattering by a finite periodic potential,'" by Roger G. Newton [AJP 62, 1042-1043(1994)]
S.K. Lamoraeaux

Physics Department, FM-15, University of Washington, Seattle, Washington 98195
(Received 5 April 1995; accepted 5 April 1995)

Am. J. Phys. Vol. 64, No. 2, Feb 1996, Pages 176
Using a retractable ball point pen to test the law of conversion of energy
Phillip Ehrlich

Department of Physics, George Mason University, Fairfax, Virginia 22030
(Received 22 May 1995; accepted 31 May 1995)

Am. J. Phys. Vol. 64, No. 2, Feb 1996, Pages 177-182
Strong focusing and the radiofrequency quadruple accelerator
Thomas P. Wrangler

Los Alamos National Laboratory, Accelerator Operations and Technology Division, Los Alamos, New Mexico 87545
(Received 19 September 1994; accepted 9 October 1995)

Am. J. Phys. Vol. 64, No. 2, Feb 1996, Pages 183-184
On the measurement of the velocity of light
Yaakov Kraftmakher

Department of Physics, Bar-Ilan University, Ramat-Gan 52900, Israel
(Received 30 March 1995; accepted 22 June 1995)

Am. J. Phys. Vol. 64, No. 2, Feb 1996, Pages 184-188
A lecture demonstration of single photon interference
Wolfgang Rueckner and Paul Titcomb

Harvard University Science center Cambridge Massachusetts 02138
(Received 28 February 1994; accepted 5 July 1995)

Am. J. Phys. Vol. 64, No. 2, Feb 1996, Pages 189-190
Cavity Quantum Elecrtodynamics
Edited by Paul R. Berman. 464 pp. Academic Press, San Diego, 1994 Price: $99.95 ISBN0-12-092245-2
Reviewed by J.H. Eberly

Am. J. Phys. Vol. 64, No. 2, Feb 1996, Pages 580-581
Classical Mechanics
Tai L. Chow. 547 pp. Wiley,New York, 1995. Price:$72.95 ISBN 0-56396-3345
Reviewed by David P. Jackson