摘要:

The Foldy–Wouthuysen transformation of the Dirac Hamiltonian is generally taught as simply a mathematical trick that allows one to obtain a two‐component theory in the low‐energy limit. It is not often emphasized that the transformed representation is the only one in which one can take a meaningfulclassicallimit, in terms of particles and antiparticles. We briefly review the history and physics of this transformation.

ISSN:0002-9505    

DOI:10.1119/1.18017

出版商:American Association of Physics Teachers    

年代:1995

数据来源: AIP

摘要:

A new statement of the second law of thermodynamics is given. The law leads almost effortlessly, for very general closed systems, to a definition of absolute entropyS, a demonstration that ΔS≥0 in adiabatic processes, a definition of temperature, and a demonstration thatdS≥δQ/Tin quasistatic processes. Entropy is given a clear physical meaning.

ISSN:0002-9505    

DOI:10.1119/1.18018

出版商:American Association of Physics Teachers    

年代:1995

数据来源: AIP

摘要:

An unconventional driven torsion pendulum influenced by gravity has been studied for chaos. Through the use of a symmetric differential capacitive sensor and a galvanometer, phase‐space trajectories were generated with anx–yrecorder. These were then later compared against output from a computer model of the system which has been further used to generate Poincaré sections, Fourier transforms, and time records. Sensitive dependence on initial conditions as a function of frequency and drive amplitude was demonstrated.

ISSN:0002-9505    

DOI:10.1119/1.18019

出版商:American Association of Physics Teachers    

年代:1995

数据来源: AIP

摘要:

We calculate the partially coherent images of an edge in one dimension by the method of adding intensities, that is, by modeling the illumination as an array of mutually incoherent plane waves incident over a range of angles. In order to visualize the transition between coherent and incoherent imaging, we display images that result from such off‐axis plane waves; these images change considerably as the angle of illumination changes. The calculations are easily carried out on a microcomputer with a high‐level mathematics program. The results shed light on off‐axis and dark‐field illumination as well. Finally, we elucidate a distinction between imaging with the aperture stop in the transform plane and imaging with the aperture stop distant from the transform plane.

ISSN:0002-9505    

DOI:10.1119/1.18020

出版商:American Association of Physics Teachers    

年代:1995

数据来源: AIP

摘要:

A method of generating analytically and numerically exact ground and excited‐state wave functions and energies of an infinite family of one‐dimensional potentials is described. Explicit application to a sixth‐order polynomial potential is presented.

ISSN:0002-9505    

DOI:10.1119/1.18021

出版商:American Association of Physics Teachers    

年代:1995

数据来源: AIP

ISSN:0002-9505    

DOI:10.1119/1.18100

出版商:American Association of Physics Teachers    

年代:1995

数据来源: AIP

ISSN:0002-9505    

DOI:10.1119/1.18096

出版商:American Association of Physics Teachers    

年代:1995

数据来源: AIP

ISSN:0002-9505    

DOI:10.1119/1.18023

出版商:American Association of Physics Teachers    

年代:1995

数据来源: AIP

ISSN:0002-9505    

DOI:10.1119/1.18024

出版商:American Association of Physics Teachers    

年代:1995

数据来源: AIP

ISSN:0002-9505    

DOI:10.1119/1.17988

出版商:American Association of Physics Teachers    

年代:1995

数据来源: AIP