摘要:

In this paper, we derive the general law for the Brownian motion displacement of a particle in a colloidal solution on the basis of a wave equation for energy, which adequately explains its vibratory character.

ISSN:0002-9505    

DOI:10.1119/1.1941807

出版商:American Association of Physics Teachers    

年代:1962

数据来源: AIP

摘要:

It is shown that the traditional methods used to derive Maxwell's equations and the boundary conditions from Coulomb's law are mathematically unsound. One widely used line of argument fails as a proof because it depends on the unwarranted extension of Maxwell's equations in integral form from the case ofNpoint charges to that of continuous volume and surface distributions of charge. The other most frequently presented argument fails because it rests on unwarranted differentiations of improper integrals and the application of Gauss' and Stokes' theorems to situations in which the standard proofs of these theorems do not hold. An alternative elementary approach is presented.

ISSN:0002-9505    

DOI:10.1119/1.1941808

出版商:American Association of Physics Teachers    

年代:1962

数据来源: AIP

摘要:

In contrast to the solution of Interior and Boundary Value Problems (IVP and BVP) in wave propagation, it is not possible to provide the simplifications made available by the Heaviside wave-expansion technique for heat conduction. The application of the Laplace transform to IVP in heat conduction generally involves the explicit application of the inversion theorem— contour integration and the evaluation of residues at poles in the complex plane. Following the presentation of solutions to some representative IVP in heat conduction in slab, cylindrical, and spherical geometry, it is shown how a heat-conduction problem in the semi-infinite domain may be reduced to a case for the finite domain. The need for the application of integral equation techniques is thus avoided. A discussion of the connection between the IVP and BVP is presented on the subject of potential theory and the phenomenon of vision as an IVP in optics.

ISSN:0002-9505    

DOI:10.1119/1.1941809

出版商:American Association of Physics Teachers    

年代:1962

数据来源: AIP

摘要:

The zeroth law of thermodynamics is shown to be a consequence of the absence of appreciable long-range forces between different portions of bodies of the kind usually under consideration in thermodynamic discussion. Revisions of the arguments given in an earlier paper are suggested in order to meet objections raised by Thomsen.

ISSN:0002-9505    

DOI:10.1119/1.1941810

出版商:American Association of Physics Teachers    

年代:1962

数据来源: AIP

摘要:

This article describes a simple apparatus for demonstrations of properties of gases and vapors requiring a mercury-filled tube. Its key features are a glass tube with a vacuum-tight valve on the top and a reservoir deep enough so the entire tube can be immersed in the mercury to expel the air. With the valve closed the tube can be used as a barometer. If some air is left in the tube, Boyle's law can be demonstrated. A simple modification of the valve allows the vapor pressure of volatile liquids to be measured.

ISSN:0002-9505    

DOI:10.1119/1.1941811

出版商:American Association of Physics Teachers    

年代:1962

数据来源: AIP

摘要:

When a fast electron passes through a thin metal film it can excite plasma oscillations which then re-radiate the energy in the form of photons. The emitted radiation will appear in a more or less sharp spectral line whose width is the sum of the intrinsic damping rate and the radiative natural line breadth. A completely equivalent formalism is provided by the extension of the theory of transition radiation (semi-infinite metal), to the case of a slab of metal bounded by two parallel planes. In the ideal case of a metal whose dielectric constant contains only a real lossless part, and no imaginary absorptive part, the predicted breadth and strength of the spectral line are the same in both theories. A further phenomenon which is suggested by the plasma-oscillation point of view is the possibility of a resonance in the reflection coefficient of a thin metal film at the plasma frequency, brought about by the collective response of the conduction electrons. The height and breadth of this resonance have been computed and should be observable in relatively ideal cases.

ISSN:0002-9505    

DOI:10.1119/1.1941812

出版商:American Association of Physics Teachers    

年代:1962

数据来源: AIP

摘要:

Two demonstrations of Kepler's third law for elliptical orbits are presented. Both assume the validity of Kepler's first two laws and a few simple facts concerning the geometry of the ellipse; one directly employs conservation of energy, the other the centripetal-force relation. But neither involves an elaborate use of the calculus.

ISSN:0002-9505    

DOI:10.1119/1.1941813

出版商:American Association of Physics Teachers    

年代:1962

数据来源: AIP

摘要:

A student experiment designed to measure the diffusion length of thermal neutrons in water is described. The technique requires only simple apparatus, demonstrates the fundamental aspects of neutron diffusion, and yields results in good agreement with the literature. Using this method the diffusion length was found to be 2.80±0.04 cm.

ISSN:0002-9505    

DOI:10.1119/1.1941814

出版商:American Association of Physics Teachers    

年代:1962

数据来源: AIP

摘要:

Some of the basic ideas of special relativity are developed through graphical representation of the results of two “thought experiments” with moving rods. The influence of the postulates of the theory on the geometric properties of the figures representing “experimental” data is described. From the figures the length contraction is derived directly. Time dilation and conservation of space-time intervals and space-time volume follow as corollaries.

ISSN:0002-9505    

DOI:10.1119/1.1941815

出版商:American Association of Physics Teachers    

年代:1962

数据来源: AIP

摘要:

It is pointed out that several conclusions ordinarily treated as being based on both the first and second laws of thermodynamics are actually dependent only on the second law. These include the efficiency of engines working between two heat reservoirs, an absolute thermometric scale, and the Clapeyron equation.

ISSN:0002-9505    

DOI:10.1119/1.1941816

出版商:American Association of Physics Teachers    

年代:1962

数据来源: AIP