ISSN:0002-9505    

DOI:10.1119/1.19018

出版商:American Association of Physics Teachers    

年代:1998

数据来源: AIP

摘要:

We discuss some of the interesting physics behind the design and operation of the Theremin electronic musical instrument. To complement the theory we present details of a parallel effort to construct two versions of this remarkable instrument. One of these designs remains fairly faithful to the traditional beat frequency oscillator approach that first inspired Theremin’s invention, while the other contains more modern electronics that helps make more reliable the setting up and use of the instrument. The emphasis on the physical principles continues into a comparison of the two instruments. Following completion, the Theremins have been extensively used in public and schools science exhibitions and in lecture demonstrations.

ISSN:0002-9505    

DOI:10.1119/1.19004

出版商:American Association of Physics Teachers    

年代:1998

数据来源: AIP

摘要:

The main features of quantum computing are described in the framework of spin resonance methods. Stress is put on the fact that quantum computing is itself nothing but a reinterpretation (fruitful indeed) of well-known concepts. The role of the two basic operations, one-spin rotation and controlled-NOT gates, is analyzed, and some exercises are proposed.

ISSN:0002-9505    

DOI:10.1119/1.19005

出版商:American Association of Physics Teachers    

年代:1998

数据来源: AIP

摘要:

Laser cooling and trapping are based on the mechanical force an electromagnetic wave (EMW) exerts upon an atom. The force is generally explained as the result of the conservation law of the linear momentum of a photon and the atom. In contrast, we have directly derived the force from primary electromagnetism in order to clarify its origin. We regarded the atom as an electric dipole moment induced by the EMW, and examined the interaction between the dipole moment and the EMW. We applied a semiclassical theory in which the atom is quantized as a two-level system but the electromagnetic field is not; no photon is introduced. The results are consistent with the commonly accepted explanation, and explicitly demonstrate the contribution of the electric and magnetic fields to the force, in particular, the significance of the longitudinal magnetic field for the dipole force in laser trapping.

ISSN:0002-9505    

DOI:10.1119/1.19006

出版商:American Association of Physics Teachers    

年代:1998

数据来源: AIP

摘要:

We discuss the use of probability theory in quantum mechanics, and suggest that there are some interpretations of quantum mechanics in which probabilities may be used inappropriately.

ISSN:0002-9505    

DOI:10.1119/1.19007

出版商:American Association of Physics Teachers    

年代:1998

数据来源: AIP

摘要:

Much has been written in recent years about the strange features associated with the quantum-mechanical description of nature at the atomic level. Physics teachers should help their students to see that many of these mysterious features are direct results of interpretive principles added to the basic theory of quantum mechanics, and that therefore they may or may not reflect the best possible understanding we can achieve of how nature works at that level. This paper discusses three such principles and their connection to well-known quantum mysteries. The practical significance of distinguishing between quantum mechanics itself and these principles is that it remains possible that other explanatory ideas may be found which lead to less mysterious consequences.

ISSN:0002-9505    

DOI:10.1119/1.19008

出版商:American Association of Physics Teachers    

年代:1998

数据来源: AIP

摘要:

A simple, one-dimensional, microscopic model of a moving body undergoing multiple collisions with particles composing a medium is introduced and solved in closed form, using energy and momentum conservation. It leads to the well-known regime of quadratic dependence on speed for the resistive force on the body.

ISSN:0002-9505    

DOI:10.1119/1.19009

出版商:American Association of Physics Teachers    

年代:1998

数据来源: AIP

摘要:

The radiative shift of the energy levels of a nonrelativistic electron in an arbitrary external potential is calculated including the effects of retardation. After mass renormalization a finite (cutoff free) expression is obtained. For the Coulomb potential the result is an expression for the Lamb shift that is as simple as that obtained by Bethe [Phys. Rev.72, 1157 (1947)] and by Welton [Phys. Rev.74, 1157 (1948)] with the neglect of retardation. As an application, a closed-form expression is given for the shift of the levels of the three-dimensional oscillator. This latter shift vanishes with the neglect of retardation.

ISSN:0002-9505    

DOI:10.1119/1.19010

出版商:American Association of Physics Teachers    

年代:1998

数据来源: AIP

摘要:

The range of stability of a vertically driven inverted pendulum is explored using simple experimental techniques. The results are found to compare well with those expected from “effective potential” theory. This vindicates the use of the theory in modeling this intriguing system.

ISSN:0002-9505    

DOI:10.1119/1.19019

出版商:American Association of Physics Teachers    

年代:1998

数据来源: AIP

摘要:

We describe an experiment in which the white-light interference fringes appearing at the output of a Michelson interferometer are observed through a spectrograph. In this manner the relative positions of monochromatic interference fringes come into sight and it allows a better understanding of the formation of the white-light fringes. A simple model is described for determining the shape of the spectrally resolved white-light interference fringes. An expression for the relationship between the slope of the fringes and the arm length difference of the interferometer is derived and is demonstrated experimentally. In addition, an intuitive explanation based on this experiment is given for the washing out of the white-light fringes.

ISSN:0002-9505    

DOI:10.1119/1.19068

出版商:American Association of Physics Teachers    

年代:1998

数据来源: AIP