摘要:

The concept of wave fronts, defined as points of like phase, can be demonstrated by the use of an audiofrequency oscillator, a loud-speaker, a microphone, and a cathode-ray oscilloscope. The shapes of wave fronts radiated from plane, line, and point sources and the attenuation of intensity with distance can be qualitatively demonstrated. The double slit diffraction pattern can be explored as a function of the wavelength, slit spacing, and distance to the plane of observation in a simple arrangement of equipment.

ISSN:0002-9505    

DOI:10.1119/1.1933116

出版商:American Association of Physics Teachers    

年代:1952

数据来源: AIP

ISSN:0002-9505    

DOI:10.1119/1.1933117

出版商:American Association of Physics Teachers    

年代:1952

数据来源: AIP

摘要:

There is a theorem due to Kramers which states that the energy states of systems with an odd number of electrons remain at least doubly degenerate in the presence of any purely electric fields. The physical significance of this theorem, its proof, and a discussion of the relationship of the Kramers degeneracy and the Wigner time-reversal operation are considered. A proof is given of the theorem that the expectation value of the magnetic moment operator is zero for any nondegenerate state.

ISSN:0002-9505    

DOI:10.1119/1.1933118

出版商:American Association of Physics Teachers    

年代:1952

数据来源: AIP

摘要:

A lecture demonstration on positron annihilation is discussed. By use of two small Geiger counters and a standard Rossi coincidence circuit, we were able to demonstrate that the two annihilation photons go in opposite directions. A special arrangement of lead shielding is suggested.

ISSN:0002-9505    

DOI:10.1119/1.1933119

出版商:American Association of Physics Teachers    

年代:1952

数据来源: AIP

摘要:

The establishment of the National Science Foundation and its anticipated impact on teaching and on basic research in the Natural Sciences are described. Two very important parts of its program are the support of basic research by grants, and the award of fellowships for predoctoral and postdoctoral study.

ISSN:0002-9505    

DOI:10.1119/1.1933120

出版商:American Association of Physics Teachers    

年代:1952

数据来源: AIP

摘要:

The generalized area-moment propositions developed by the author are combined with the principle of superposition to produce an alternative set of generalized area-moment propositions, which are extremely simple and convenient in application. The method is illustrated by treating in detail two standard cases in beam theory. The method can also be applied advantageously to the solution of statically indeterminate beams.

ISSN:0002-9505    

DOI:10.1119/1.1933121

出版商:American Association of Physics Teachers    

年代:1952

数据来源: AIP

摘要:

Microwave resonance absorption inCr2O3, MnO,MnF2, and CoO above and below the paramagnetic-antiferromagnetic transition temperature is reviewed. The amount of the absorption decreases abruptly in lowering the temperature of the sample through its Curie temperature. The nature of the crystal structure changes associated with the changes in magnetic structure are given for comparison. With the exception of CoO, the alignment of magnetic ions to form the antiferromagnetic configuration results in a deformation along an axis perpendicular to sheets of magnetic ions having parallel spins. Similar results are reported for magnetite.

ISSN:0002-9505    

DOI:10.1119/1.1933122

出版商:American Association of Physics Teachers    

年代:1952

数据来源: AIP

摘要:

An effort is made to show that the concept of pressure in an incompressible fluid as energy per unit volume possessed by the fluid is an erroneous one, and that Bernoulli's equation is not to be interpreted as a statement of conservation of energy, but rather as a relation between pressure, velocity, and height in the gravitational field.

ISSN:0002-9505    

DOI:10.1119/1.1933123

出版商:American Association of Physics Teachers    

年代:1952

数据来源: AIP

摘要:

The paper presents the concepts involved in the study of adsorption of gases on solids. Particular stress is placed on the problem of uniform surfaces. An historical study follows which is specifically concerned with (1) metal filaments and evaporated films and (2) surfaces of metal single crystals, both considered as approximations to ideal surfaces for adsorption measurements.

ISSN:0002-9505    

DOI:10.1119/1.1933124

出版商:American Association of Physics Teachers    

年代:1952

数据来源: AIP

摘要:

A survey of staff available, space and library facilities, and research budgets of physics departments in American universities is summarized. Fields of study in institutions offering the Ph.D. and M.S. degrees are itemized.

ISSN:0002-9505    

DOI:10.1119/1.1933125

出版商:American Association of Physics Teachers    

年代:1952

数据来源: AIP