摘要:

The transmission of a Dirac particle through a high (V0>E+m) square electrostatic potential barrier is investigated further. As is well known, the transmission coefficient is nonzero even asV0goes to infinity. As well as reproducing the usual wave mechanics approach, a detailed fermion–antifermion multiple scattering calculation and anS‐matrix calculation are examined to provide additional insight into the problem. The origin of the curious behavior is found to be the result of pair creation and annihilation events.

ISSN:0002-9505    

DOI:10.1119/1.16546

出版商:American Association of Physics Teachers    

年代:1991

数据来源: AIP

摘要:

An inexpensive, easy to build gas effusion apparatus for measuring molecular velocities is described. The instrument features a liquid nitrogen cooled adsorption pump to replace more costly diffusion and rotary vacuum pumps. Low cost, low maintenance, and simplicity of operation render the experiment suitable for introductory physics students. A straightforward measurement consistently yields average velocities within 10% of the calculated values.

ISSN:0002-9505    

DOI:10.1119/1.16547

出版商:American Association of Physics Teachers    

年代:1991

数据来源: AIP

摘要:

This paper represents an extension of the results of an original paper on the subject [Am. J. Phys.57, 654–657 (1989)]. Here an experiment, originally performed by Titcombetal., to demonstrate the inverse sprinkler effect is described and analyzed. It is shown that, in a water reservoir, the angular momentum of the sprinkler head is approximately equal and opposite that of the fluid in the sprinkler arms. However, in an air reservoir, one must consider the effects of both turbulence and the motion of the reservoir. Both effects result in a steady‐state acceleration of the inverse sprinkler in a direction opposite that of the normal sprinkler. Also presented is a more detailed analysis than the one given in the original paper to explain the steady‐state behavior of the inverse sprinkler.

ISSN:0002-9505    

DOI:10.1119/1.16548

出版商:American Association of Physics Teachers    

年代:1991

数据来源: AIP

摘要:

It is suggested that error analysis in elementary laboratories be carried out by computer simulation of repeated measurements. Results should be represented as histograms. This procedure is concrete and correct, and makes definite and graphic what is meant by ‘‘error analysis.’’

ISSN:0002-9505    

DOI:10.1119/1.16549

出版商:American Association of Physics Teachers    

年代:1991

数据来源: AIP

摘要:

The problem of effusion of a dilute gas through a hole by means of van Kampen’s systematic Ω expansion has been studied. In this way, the macroscopic equation as well as the Fokker–Planck equation for the fluctuations around the macroscopic behavior have been obtained and some dubious points in a recent analysis of the problem clarified.

ISSN:0002-9505    

DOI:10.1119/1.16832

出版商:American Association of Physics Teachers    

年代:1991

数据来源: AIP

摘要:

A general education course in astronomy was successfully adapted to provide a meaningful laboratory science experience for a visually‐impaired student. Minor alterations to the style of lecture, coupled with an edition of the text on audio cassette tapes, allowed the student to keep pace with the theory component of the course. Laboratory equipment was modified to provide tactile measuring apparatus, which allowed the student to perform all the same processes of data acquisition and analysis required of sighted students.

ISSN:0002-9505    

DOI:10.1119/1.16550

出版商:American Association of Physics Teachers    

年代:1991

数据来源: AIP

摘要:

The conditions of local gauge invariance under a general non‐Abelian group are discussed. They imply the field equations for the gauge vector fields and the existence of conserved Noether’s currents of global gauge invariance. There are no extra conserved currents associated with local gauge invariance.

ISSN:0002-9505    

DOI:10.1119/1.16551

出版商:American Association of Physics Teachers    

年代:1991

数据来源: AIP

ISSN:0002-9505    

DOI:10.1119/1.16552

出版商:American Association of Physics Teachers    

年代:1991

数据来源: AIP

ISSN:0002-9505    

DOI:10.1119/1.16553

出版商:American Association of Physics Teachers    

年代:1991

数据来源: AIP

ISSN:0002-9505    

DOI:10.1119/1.16554

出版商:American Association of Physics Teachers    

年代:1991

数据来源: AIP