ISSN:0002-9505    

DOI:10.1119/1.17402

出版商:American Association of Physics Teachers    

年代:1993

数据来源: AIP

摘要:

This Resource Letter provides a guide to the literature on radio pulsars. Papers at elementary (E), intermediate (I), and advanced (A) levels are cited. Historically important papers, including relevant articles published before the discovery of pulsars in 1967, are listed, as are current areas of pulsar research. This guide also includes a discussion of pulsars’ use in studying a variety of other phenomena ranging from the interstellar medium to relativistic theories of gravitation.

ISSN:0002-9505    

DOI:10.1119/1.17403

出版商:American Association of Physics Teachers    

年代:1993

数据来源: AIP

摘要:

The ability of the spherical step potential well to model the Ramsauer–Townsend effect, the near disappearance of low‐energy electron scattering in the noble gases argon, krypton, and xenon, is discussed. It is shown that conditions can be found for which the cross section vanishes as the energy approaches zero, but that the noble gas phenomenon, where the cross sections show sharp minima at finite energies, cannot be modeled. The low‐energys‐wave cross section can be made to vanish, but thep‐wave cross section rises too rapidly with energy to permit a minimum in the total cross section. In addition it is shown that the condition for the vanishing of thes‐wave cross section at zero or low energy also implies the occurrence of ad‐wave resonance at zero or low energy. In the noble gases, the polarization term appears to be the essential feature of the atomic potential which gives rise to the effect.

ISSN:0002-9505    

DOI:10.1119/1.17404

出版商:American Association of Physics Teachers    

年代:1993

数据来源: AIP

摘要:

The wave functions in momentum space for discrete states of hydrogenlike atoms are discussed in terms of both the early contributions to the subject and their present usefulness in atomic physics. The derivation of some of their important properties is outlined, in particular the expectation values of various powers of momentum and kinetic energy, and the kinetic energy distribution. As an application, the cross section for ionization of hydrogen in the metastable 2Sstate by electron impact is calculated with the aid of the binary‐encounter approximation, which requires the use of momentum‐space wave functions.

ISSN:0002-9505    

DOI:10.1119/1.17405

出版商:American Association of Physics Teachers    

年代:1993

数据来源: AIP

摘要:

The sharp peaks present in the diffraction pattern of a one‐dimensional Fibonacci quasicrystal are explained physically. The explanation rests upon the discovery of periodically positioned spatial regions, with mutually incommensurable spacings, which completely or partially exclude the atoms of the quasicrystal. These sets of periodic exclusion zones act individually as gratings. A ruler‐like optical analog of a 1‐D quasicrystal, in which grating lines replace the hypothetical atoms of the quasicrystal, provides an opportunity to observe quasicrystal diffraction directly. Such a grating can be produced by hand with simple equipment.

ISSN:0002-9505    

DOI:10.1119/1.17406

出版商:American Association of Physics Teachers    

年代:1993

数据来源: AIP

摘要:

The well‐known image method for a conducting sphere in front of an electrostatic source, due to Lord Kelvin from 1848, is generalized for electrostatic problems involving a dielectric sphere and for magnetostatic problems involving a permeable sphere. It is seen that the image sources are very simple, for a point source they consist of a point source plus a line source obeying a simple power law. The expressions are checked to satisfy all known limit cases. The image theory can be applied with simple computing devices for static or quasistatic problems involving material spheres.

ISSN:0002-9505    

DOI:10.1119/1.17407

出版商:American Association of Physics Teachers    

年代:1993

数据来源: AIP

摘要:

Coupled‐amplitude equations are used widely to analyze problems involving wave propagation. The free‐space Green’s function can be used to advantage to show that these equations emerge naturally from the wave equation. The procedure for obtaining the coupled‐amplitude equations is an instructive one that will likely prove a useful addition to the list of examples of the practical utility of Green’s functions.

ISSN:0002-9505    

DOI:10.1119/1.17408

出版商:American Association of Physics Teachers    

年代:1993

数据来源: AIP

摘要:

Cellular automata and neural nets are nonlinear dynamical systems of interest to physicists as models of computational devices and physical processes. The possible states of bothN‐cell automata andN‐binary‐neuron networks can be represented by the 2Ncorners of the unit hypercube (the Hamming set) inN‐dimensional space. This representation is transparently related to the representation of the states ofNspin‐one‐half particle systems and ofN‐step random walks by strings of positive and negative ones (the Ising set). The dynamics of discrete neural networks and cellular automata can be described by the 2Nby 2Ntransition matrices which describe the mappings of the Hamming set and Ising set into themselves. This representation renders some properties of these nonlinear systems readily apparent, and highlights their relation to the lattice gas, systems of interacting spins, and the random walk.

ISSN:0002-9505    

DOI:10.1119/1.17409

出版商:American Association of Physics Teachers    

年代:1993

数据来源: AIP

摘要:

The model of two boxes in thermal contact each filled with an ideal quasiclassical gas is used to treat, in a unified way, temperature fluctuations in both finite and infinite heat baths. One box is regarded as the heat bath and the other serves as the thermometer.

ISSN:0002-9505    

DOI:10.1119/1.17410

出版商:American Association of Physics Teachers    

年代:1993

数据来源: AIP

摘要:

In the case of singular forces, for which some of the higher derivatives do not exist at a given point, it is not generally true that Newton’s equations of motion will give unique solutions for given initial conditions. In this paper, the motion of a particle in a one‐dimensional conservative force field is considered. The necessary and sufficient conditions that ensure unique solutions are determined.

ISSN:0002-9505    

DOI:10.1119/1.17411

出版商:American Association of Physics Teachers    

年代:1993

数据来源: AIP