摘要:

A discussion is given of the methods that have been used in ultrasonic attenuation studies, with block diagrams of several experimental setups. Sources of internal friction in metals are mentioned and a brief discussion of magnetoacoustic measurements is given. Measurements on nonmetallic crystals and glasses at gigacycle frequencies and the amplification of ultra sound in semiconductors are briefly considered.

ISSN:0002-9505    

DOI:10.1119/1.1970758

出版商:American Association of Physics Teachers    

年代:1964

数据来源: AIP

摘要:

Thermodynamical properties of a gaseous mixture undergoing dissociation or ionization, or both, have been considered in a general way. As a special case, the behavior of ionizing hydrogen gas has been studied. It is found that a perfect gas behaves as an imperfect gas in many ways, when undergoing dissociation or ionization.

ISSN:0002-9505    

DOI:10.1119/1.1970760

出版商:American Association of Physics Teachers    

年代:1964

数据来源: AIP

摘要:

We present the design of a simple rotating-disk viscometer that can be actuated while under a bell-jar to measure the viscosity of a gas as a function of pressure. The instrument is designed to provide an interesting application of the kinetic theory of gasses for an introductory physics laboratory.

ISSN:0002-9505    

DOI:10.1119/1.1970762

出版商:American Association of Physics Teachers    

年代:1964

数据来源: AIP

摘要:

Bethe's early group-theoretical treatment is supplemented by some physical arguments illustrating his method of semiquantitative evaluation of the term splitting. Up to date notations are introduced. The cases of weak, intermediate, and strong crystal-field splitting are discussed, with typical ions given as examples. For cubic and hexagonal site symmetry, the Bethe method is demonstrated step-by-step and the results applied to transition metal ions. Double-valued group representations, double groups and Kramers degeneracy are introduced, compared, and illustrated with physical examples. Certain mathematical analogies between formulas of representation theory and angular momentum theory are pointed out.

ISSN:0002-9505    

DOI:10.1119/1.1970764

出版商:American Association of Physics Teachers    

年代:1964

数据来源: AIP

摘要:

The WKB method of solution to Schrödinger's equation is usually applied individually to partial waves of definite angular momentum, i.e., in one dimension. However, the partial differential equation may be solved directly, by this method, and the first two terms are derived for the solution to scattering by a central potential. The resulting cross section is the same as in classical theory.

ISSN:0002-9505    

DOI:10.1119/1.1970766

出版商:American Association of Physics Teachers    

年代:1964

数据来源: AIP

摘要:

A radio interferometer has been constructed at Haverford College as an aid to learning the fundamentals of radio astronomy. Its cost, both in cash outlay and in construction time, make it a feasible year-long project for an undergraduate. Its simplicity does not prevent it from being a useful instrument for instruction at the college or high-school level; among its capabilities are the measurement of the positions of at least four of the strongest discrete cosmic-noise sources, and the diameter of the radio sun.

ISSN:0002-9505    

DOI:10.1119/1.1970768

出版商:American Association of Physics Teachers    

年代:1964

数据来源: AIP

摘要:

Using a Van de Graaff electrostatic generator and a linear accelerator, the speeds of electrons with kinetic energies in the range 0.5–15 MeV are determined by measuring the time requiredfor the electrons to traverse a given distance. The measurements show the existence of a limiting speed in accord with the results of special relativity. The kinetic energy, determined by calorimetry,verifies that an electric field exerts a force on a moving electron in its direction of motion that is independent of its speed.

ISSN:0002-9505    

DOI:10.1119/1.1970770

出版商:American Association of Physics Teachers    

年代:1964

数据来源: AIP

摘要:

The electrical and optical properties of an ionized gas are derived from a simple physical consideration, based on the average energy acquired by an electron between collisions. The correct formulas are obtained if a time-dependent collision frequency is employed.

ISSN:0002-9505    

DOI:10.1119/1.1970772

出版商:American Association of Physics Teachers    

年代:1964

数据来源: AIP

摘要:

A relation between the generalized Foldy-Wouthuysen, presented in a preceding paper, and the special Lorentz transformations is shown.

ISSN:0002-9505    

DOI:10.1119/1.1970774

出版商:American Association of Physics Teachers    

年代:1964

数据来源: AIP

摘要:

Some of the problems posed in this paper have been passed around the scientific community for several years and have served to jar a good many scientists regarding their intuition for statistical events. Since these problems are part of the scientific folklore, it seems worthwhile to write them down. The informal narrative style used reflects an attempt to capture a part of the spirit of the usual oral presentation. The author has added some additional questions and methods of solution that have arisen in presenting the problems to informal colloquiums.

ISSN:0002-9505    

DOI:10.1119/1.1970776

出版商:American Association of Physics Teachers    

年代:1964

数据来源: AIP