ISSN:0002-9505    

DOI:10.1119/1.11712

出版商:American Association of Physics Teachers    

年代:1979

数据来源: AIP

ISSN:0002-9505    

DOI:10.1119/1.11714

出版商:American Association of Physics Teachers    

年代:1979

数据来源: AIP

ISSN:0002-9505    

DOI:10.1119/1.11715

出版商:American Association of Physics Teachers    

年代:1979

数据来源: AIP

ISSN:0002-9505    

DOI:10.1119/1.11716

出版商:American Association of Physics Teachers    

年代:1979

数据来源: AIP

ISSN:0002-9505    

DOI:10.1119/1.11717

出版商:American Association of Physics Teachers    

年代:1979

数据来源: AIP

摘要:

In Brownian motion the ensemble average of the product of the displacement and the random force is zero. This result was assumed by Langevin to be true, although it appears to contradict the intuitive feeling that the net displacement should be in the direction of the net impulse. The literature contains a statement that the Langevin assumption is incorrect, and this led us to an examination of the question. We show that the relevant correlation function in one dimension is 〈x(t)A(t−τ) 〉=2(kBT/M)[1−exp(−βτ)] which is zero at equal times and approaches 2(kBT/M) as τ→∞.

ISSN:0002-9505    

DOI:10.1119/1.11719

出版商:American Association of Physics Teachers    

年代:1979

数据来源: AIP

摘要:

Simple apparatus for producing strip holograms is described. Moving the object slightly between exposures permits motion to be simulated, analogously to an animated motion picture. The resulting hologram is viewed by scanning the eyes vertically across the slits. The hologram maintains full horizontal parallax, but the slit aperture reduces the vertical viewing angle of the animated object.

ISSN:0002-9505    

DOI:10.1119/1.11720

出版商:American Association of Physics Teachers    

年代:1979

数据来源: AIP

摘要:

The relationship between the energy derivative of the Coulomb phase shift and the classical expression for the time delay is discussed.

ISSN:0002-9505    

DOI:10.1119/1.11721

出版商:American Association of Physics Teachers    

年代:1979

数据来源: AIP

摘要:

A tropical year is usually described incorrectly as the actual interval between two successive passages of the Sun through the vernal equinox. These intervals vary from year to year because of the differing periods of the perturbations of the angular velocity of the Earth. A tropical year is correctly defined as the mean interval between two successive passages of the Sun through the mean equinox of date. The time of beginning of spring depends on (i) the perturbations of the angular velocity of the Earth, (ii) the nutation of the Earth’s axis, and (iii) the aberration of light.

ISSN:0002-9505    

DOI:10.1119/1.11742

出版商:American Association of Physics Teachers    

年代:1979

数据来源: AIP

摘要:

The propagation of a steplike change in the amplitude of a dc pulse and a step in the envelope of a plane sinusoidal wave are investigated. It is shown that a step (e.g., the beginning or end of a pulse or wave) propagates like a pulse in the medium; i.e., its velocity is a weighted average of the group velocity, and its rate of spread is determined by the distribution of group velocities within the spectrum of the step. The results apply to a real pulse (e.g., sound) in an infinite, homogeneous, dispersive, lossless medium, and to the quantum‐mechanical wave function of a free particle.

ISSN:0002-9505    

DOI:10.1119/1.11743

出版商:American Association of Physics Teachers    

年代:1979

数据来源: AIP