摘要:

An elementary description of polarization phenomena involving spin-1/2particles is given. With the aid of schematic diagrams, the relation between analyzing power and polarization is obtained. Single and double scattering by spin-0 nuclei and depolarization effects in the scattering by nuclei with spin are discussed. A brief treatment of polarization phenomena in reactions is presented.

ISSN:0002-9505    

DOI:10.1119/1.1973905

出版商:American Association of Physics Teachers    

年代:1967

数据来源: AIP

摘要:

A transient electrical discharge in air serves as a convenient source of acoustic impulses for studies of wave diffraction. “Nwaves,” with initial shocks about 0.01 atm in magnitude and with durations of less than 30 μsec at 10 cm distance, are produced by sparks having discharge energies of 0.05 J. They are detected with wide-band condenser microphones, which utilize a14-mil metallized Mylar diaphragm supported partially by the thin layer of air trapped on a machined brass surface. The receiving response is nominally flat to above12MHz. Phenomena which are demonstrated here include the diffraction ofNwaves incident upon circular disks and narrow rectangular plates.

ISSN:0002-9505    

DOI:10.1119/1.1973907

出版商:American Association of Physics Teachers    

年代:1967

数据来源: AIP

摘要:

Resonance of a confined plasma magnetized by a dipole field is a fundamental geophysical problem which, except for special cases, remains unsolved. As an introduction to the equations, formalism, and concepts to be encountered in the more difficult dipole case, the problem of resonance in a plasma magnetized by a monopole or, in general, radial magnetic field has been solved. The magnetohydrodynamic wave equation is derived, and its plane wave solutions are indicated. For the case of a radial magnetic field, both axisymmetric and nonaxisymmetric solutions are obtained. Finally, the concept of vibrating magnetic-field lines is derived and discussed.

ISSN:0002-9505    

DOI:10.1119/1.1973909

出版商:American Association of Physics Teachers    

年代:1967

数据来源: AIP

摘要:

Expressions are derived for the electromagnetic fields of guided waves which are analogous to the quantum-mechanical equations representing barrier tunneling. This analogy is achieved by comparing the propagation constant of the Schrödinger time-independent wave equation with that of the electromagnetic wave equation in waveguide and by comparing the de Broglie wavelength of a particle with the wavelength of the waves that propagate the energy. This results in an expression relating the form of an arbitrary one-dimensional energy barrier to the physical dimensions of a section of waveguide. The analogy is tested by the propagation of energy in theTE10mode at both the 3- and 6-cm bands for the cases of rectangular and hyperbolic barriers. Although evanescent modes are present at the discontinuous regions, the analog for the rectangular barrier, which is considered to be the worse case, is verified when an effective barrier lengthleffof about 1.2lis used. This experimental verification demonstrates the possibility of waveguide simulation of quantum-mechanical energy barriers and the practicality of utilizing an electromagnetic analog for demonstrating the tunneling phenomenon and provides a method for measurement of the transmission coefficient through an arbitrarily shaped barrier.

ISSN:0002-9505    

DOI:10.1119/1.1973911

出版商:American Association of Physics Teachers    

年代:1967

数据来源: AIP

摘要:

Charles Glover Barkla (1877–1944) was one of the early pioneers in x-ray research. His most important contributions were those showing that x rays could be polarized; that when x-rays were scattered by light atoms the number of electrons in the atoms was about half their atomic weight, and that when x rays were incident on heavy atoms these atoms emitted characteristic or fluorescent radiations, which he called theKandLseries. He explained the latter in terms of the Rutherford-Bohr atom. For the discovery of the characteristic radiations, he was awarded the Nobel prize in 1917. Shortly before this time, he considered that he had discovered a new type of characteristic radiation which he calledJradiation, later modifying the description toJtransformation. Though a great deal of work was done on thisJradiation, he was not really able to substantiate its existence. He essentially never modified his early ideas or apparatus, although important discoveries were being made in x rays by Bragg, Compton, Auger, and others.

ISSN:0002-9505    

DOI:10.1119/1.1973913

出版商:American Association of Physics Teachers    

年代:1967

数据来源: AIP

摘要:

Even in static fields, where there is no observable energy flow, Poynting vector momentum must be considered to avoid an apparent violation of the angular-momentum law. This often-neglected aspect of the Poynting vector, is illustrated in an easily calculated example. Two other simple and rigorously solvable pedagogical examples illustrate the role of the Poynting vector in defining the energy flow in static fields.

ISSN:0002-9505    

DOI:10.1119/1.1973915

出版商:American Association of Physics Teachers    

年代:1967

数据来源: AIP

ISSN:0002-9505    

DOI:10.1119/1.1973919

出版商:American Association of Physics Teachers    

年代:1967

数据来源: AIP

ISSN:0002-9505    

DOI:10.1119/1.1973924

出版商:American Association of Physics Teachers    

年代:1967

数据来源: AIP

ISSN:0002-9505    

DOI:10.1119/1.1973926

出版商:American Association of Physics Teachers    

年代:1967

数据来源: AIP

ISSN:0002-9505    

DOI:10.1119/1.1973928

出版商:American Association of Physics Teachers    

年代:1967

数据来源: AIP