ISSN:0002-9505    

DOI:10.1119/1.17286

出版商:American Association of Physics Teachers    

年代:1993

数据来源: AIP

ISSN:0002-9505    

DOI:10.1119/1.17289

出版商:American Association of Physics Teachers    

年代:1993

数据来源: AIP

ISSN:0002-9505    

DOI:10.1119/1.17290

出版商:American Association of Physics Teachers    

年代:1993

数据来源: AIP

摘要:

The idea of a laser driven space vehicle capable of interinterstellar travel was raised 25 years ago. The original article by Marx [Nature211, 22–23 (1966)] presented a relativistic calculation that contained conceptual and numerical errors. Here the inconsistencies of the original article are corrected. Marx’s calculations are generalized to the case where the laser is of variable power, and to the interesting case where the laser beam is recycled by means of mirrors. The obstacles to this form of interstellar travel appear insurmountable, but the calculations provide an excellent example of the application of relativistic ideas.

ISSN:0002-9505    

DOI:10.1119/1.17291

出版商:American Association of Physics Teachers    

年代:1993

数据来源: AIP

摘要:

Small telescopes equipped with charge‐coupled device (CCD) imaging cameras are well suited to introductory laboratory exercises in positional astronomy (astrometry). An elegant example is the determination of the parallax of extraterrestrial objects, such as asteroids. For laboratory exercises suitable for introductory students, the astronomical hardware needs are relatively modest, and, under the best circumstances, the analysis requires little more than arithmetic and a microcomputer with image display capabilities. Results from the first such coordinated parallax observations of asteroids ever made are presented. In addition, procedures for several related experiments, involving single‐site observations and/or parallaxes of earth‐orbiting artificial satellites, are outlined.

ISSN:0002-9505    

DOI:10.1119/1.17292

出版商:American Association of Physics Teachers    

年代:1993

数据来源: AIP

摘要:

Some insights into gravitation and mechanics, as well as some surprises, result from considering the dynamics of negative mass particles.

ISSN:0002-9505    

DOI:10.1119/1.17293

出版商:American Association of Physics Teachers    

年代:1993

数据来源: AIP

摘要:

Retarded fields are used for deriving the force exerted on a stationary charge by a slowly moving current‐carrying conductor or a slowly moving magnet. The derivation makes use of the fact that a neutral current‐carrying conductor, when it is moving, creates an external electric field. Although the presence of this field is generally regarded as a strictly relativistic effect, it is shown that this field is deducible from the basic laws of classical electrodynamics, without any recourse to relativity. In terms of classical electrodynamics, a moving neutral current‐carrying conductor creates this electric field because of unequal retardation of the electric potentials associated with the positive and negative charges of the conductor. This field must be taken into account for the correct computation of the force exerted by moving current‐carrying conductor or a moving magnet on a stationary charge.

ISSN:0002-9505    

DOI:10.1119/1.17294

出版商:American Association of Physics Teachers    

年代:1993

数据来源: AIP

摘要:

Since 1983, the Maryland University Project in Physics and Educational Technology (M.U.P.P.E.T.) has been investigating the implication of including student programming in an introductory physics course for physics majors. Many significant changes can result. One can rearrange some content to be more physically appropriate, include more realistic problems, and introduce some contemporary topics. One can begin training the student in professional research‐related skills at an earlier stage than is traditional. An interesting point to note is that the inclusion of carefully considered computer content requires an increased emphasis on qualitative and analytic thinking.  

ISSN:0002-9505    

DOI:10.1119/1.17295

出版商:American Association of Physics Teachers    

年代:1993

数据来源: AIP

摘要:

A straightforward procedure is presented to derive the propagator in simple quantum systems. This approach enables us to define a state which behaves as a generalization of the well‐known coherent state of the harmonic oscillator.

ISSN:0002-9505    

DOI:10.1119/1.17296

出版商:American Association of Physics Teachers    

年代:1993

数据来源: AIP

摘要:

Using a simple geometrical construction ink‐space and a ray‐tracing procedure, the overall nature of the phase conjugation process is examined. The usefulness of thek‐space formalism and the ray‐tracing procedure as instructional tools is demonstrated by analyzing various cases.

ISSN:0002-9505    

DOI:10.1119/1.17297

出版商:American Association of Physics Teachers    

年代:1993

数据来源: AIP