ISSN:0002-9505    

DOI:10.1119/1.18281

出版商:American Association of Physics Teachers    

年代:1996

数据来源: AIP

ISSN:0002-9505    

DOI:10.1119/1.18313

出版商:American Association of Physics Teachers    

年代:1996

数据来源: AIP

摘要:

This Resource Letter provides a guide to the literature on the interaction of extremely low‐frequency electromagnetic field (ELF/EMF) interactions with biological matter, and on the possibility that such interactions could have a harmful effect on human health. Journal articles and books are cited for the following topics: ELF/EMF theoretical interactions with biological cells, organs and organisms, magnetic dipole interactions, sensing by animals, biomedical–biophysical experiments, epidemiology, and litigation–mitigation risk issues.

ISSN:0002-9505    

DOI:10.1119/1.18314

出版商:American Association of Physics Teachers    

年代:1996

数据来源: AIP

摘要:

Many electrical and mechanical systems with two normal modes are appropriate for illustrating the quantum mechanics of neutral kaons. The illustration of CP‐ or time‐reversal violation in the neutral kaon system by mechanical or electrical analogues is more subtle. Some possibilities which could be realized in a tabletop demonstration are suggested.

ISSN:0002-9505    

DOI:10.1119/1.18472

出版商:American Association of Physics Teachers    

年代:1996

数据来源: AIP

摘要:

We describe how the reflection and transmission of light at a dielectric interface can be understood starting from the fact that dielectrics are collections of molecules. More precisely, we consider from the microscopic perspective the interpretation and significance of the Ewald–Oseen extinction theorem of classical optics. The usual interpretation of the theorem is that an incident field is extinguished by the dipoles on the boundary and replaced by transmitted and reflected fields consistent with the Maxwell equations for the media. However, the extinction theorem is more appropriately regarded simply as a boundary condition effected byallthe molecular scatterers, not just those at the boundary. To demonstrate this we take a microscopic approach to three familiar problems: (1) the electrostatic interaction of a point charge with a dielectric wall; (2) the reflection of a monochromatic plane wave at a dielectric interface; and (3) diffraction by an aperture. We show that the extinction of the incident field cannot be attributed to any finite dipole boundary layer, and in particular it does not involve any ‘‘extinction theorem distance.’’

ISSN:0002-9505    

DOI:10.1119/1.18315

出版商:American Association of Physics Teachers    

年代:1996

数据来源: AIP

摘要:

A majority of introductory calculus‐based physics textbooks, including many widely used ones, give misleading or incorrect explanations for the failure of the equipartition law to describe correctly the classically expected rotational degrees of freedom in monatomic and diatomic gases. This article outlines typical textbook treatments and reviews the quantum mechanical explanation.

ISSN:0002-9505    

DOI:10.1119/1.18316

出版商:American Association of Physics Teachers    

年代:1996

数据来源: AIP

摘要:

The determination of the reactions on a ladder is discussed including friction against the wall. In a recent article, this problem was studied considering elastic compression and it was argued that an additional condition holds that allows one to find all the reactions. We show that this condition is incorrect for typical ladders, when flexion is important. We clarify the issues of static determinacy by means of an analysis that takes into account both compression and flexion. We find that when the climber arrives at the top, the result depends on which deformation prevails. We conclude that the reactions can never be determined using only statics, because there is no way to ascertain which kind of deformation dominates, and so which limiting condition will be attained, if any.

ISSN:0002-9505    

DOI:10.1119/1.18317

出版商:American Association of Physics Teachers    

年代:1996

数据来源: AIP

摘要:

We present a variation and extension of the twin paradox recently put forth by Boughn. These additional considerations make a strong case that there is no meaning to the question of ‘‘where’’ the aging difference occurs in the twin paradox.

ISSN:0002-9505    

DOI:10.1119/1.18318

出版商:American Association of Physics Teachers    

年代:1996

数据来源: AIP

摘要:

The electric and magnetic fields for a hollow conducting sphere located in a slowly varying uniform electric field background are computed to first‐order in a power series expansion in the field frequency. These results are used to define an equivalent RC circuit and to test the circuit approach which is often used in electromagnetic compatibility (EMC). The case of an infinite cylindrical conducting tube under the influence of the same external field is also analyzed.

ISSN:0002-9505    

DOI:10.1119/1.18319

出版商:American Association of Physics Teachers    

年代:1996

数据来源: AIP

摘要:

In this paper, we introduce a classical model for the behavior of the outer electron of a Rydberg helium atom in both static and time‐dependent electric fields; we contrast the behavior of this dynamical system with the behavior of the classical model for highly excited hydrogen atoms in similar fields; and we show that these classical models recover many features of the system that would seem to be purely quantal in origin. Perhaps the most surprising of these is the apparent presence of ‘‘classical avoided crossings’’ in the Stark energy level structure of the classical helium model. Finally, we compare the behavior of our helium model to experimental data obtained by Koch, Mariani, and co‐workers in their investigations of the ionization of highly excited helium atoms in a microwave field, and we note the agreement between experiment and theory.

ISSN:0002-9505    

DOI:10.1119/1.18320

出版商:American Association of Physics Teachers    

年代:1996

数据来源: AIP