摘要:

The photoelastic effect in amorphous solids is caused by two effects. The elastic deformations alter the Lorentz‐Lorenz interaction between the dipoles, and in addition produce optical anisotropy of the atoms. For pressure the first effect creates positive birefringence, while the second effect gives negative birefringence. In most cases the second effect is larger. With increasing index of refraction the first effect increases faster than the second effect, and hence the photoelastic constants decrease and reversal of sign occurs. Measurements on glasses verify the theory. A uniform volume expansion of 1 percent increases the refraction of the oxygen ions by 0.4 percent and a strain of 1 percent creates an optical anisotropy of the 0 ion of about 0.7 percent. For the positive ions these effects are somewhat smaller.

ISSN:0021-8979    

DOI:10.1063/1.1745316

出版商:AIP    

年代:1935

数据来源: AIP

摘要:

The movement of ferromagnetic particles in various types of alternating magnetic fields and the mechanisms involved are discussed. The conditions under which demagnetization takes place in magnetic fields produced by damped high frequency oscillatory discharges are described, and possible practical applications to the magnetic separation of ores and to routine laboratory magnetic testing of iron and steel are indicated.

ISSN:0021-8979    

DOI:10.1063/1.1745317

出版商:AIP    

年代:1935

数据来源: AIP

摘要:

The dependence of the velocity of sound on gas temtemperatures is utilized to determine the temperature of the copper arc in air at atmospheric pressure. The sound ``wave'' produced from a condensed spark discharge in air is passed through the stabilized arc column and received by a second spark discharge, acting as a microphone. The time interval is measured on the cathode‐ray oscillograph. When the arc length and, hence, sound path, are varied, the time interval varies approximately linearly. The resultant sound velocity free from end corrections is 1.39×105cm sec.−1, for which the arc temperature is calculated to be 4100±300°K when corrections for dissociation and changes in specific heat are taken into account. Time intervals are measured for a constant arc length of 9 cm for currents between 3 and 26 amperes, and it is found that the velocity (and temperature) is independent of current within the experimental error. Conclusions based on the results are: (1) The electron density is 0.6×1012; (2), the partial pressure of Cu vapor is 7.5×10−7; and (3), the ``effective ionization potential'' of the arc gas is 12.3 volts.

ISSN:0021-8979    

DOI:10.1063/1.1745318

出版商:AIP    

年代:1935

数据来源: AIP

摘要:

Experimentally determined values of the velocitycof sound in atmospheric pressure arcs in air are interpreted in terms of the temperature of the gas. The velocity may be expressed in general in the form:c=((RT/M)(1+R/Cv))12,which applies to pure gases or mixtures of gases that obey the perfect gas laws. In this relationTis the absolute temperature;Mis the mean molecular weight defined as:M=&Sgr;Mipi/&Sgr;pi;Cvis the specific heat (per gram molecule) defined as:Cv=&Sgr;(Cv)ipi/&Sgr;pi, where the summation is taken for all the gas components present. In the case of the arc in air, the components considered are the undissociated and dissociated oxygen and nitrogen. The values for the specific heat and degree of dissociation, taken from the equilibrium calculations of H. L. Johnston and associates are used, care being taken to apply the correct partial pressures. Possible sources of error due to thermal diffusion and other causes are considered.

ISSN:0021-8979    

DOI:10.1063/1.1745319

出版商:AIP    

年代:1935

数据来源: AIP

摘要:

The photoelectric emission from a platinum filament coated with thorium oxide seems to be due chiefly to that part of the spectrum lying between 2500A and 3100A. An increase in the photoelectric emission from the thorium‐oxide‐coated platinum filament was observed with increasing temperature from 23°C up to about 200°C, and a decrease from the same filament with increasing temperature from 200°C to about 400°C. A definite photoelectric emission was observed from this filament whether the corresponding thermionic current was saturated or not. No photoelectric fatigue was observed.

ISSN:0021-8979    

DOI:10.1063/1.1745320

出版商:AIP    

年代:1935

数据来源: AIP

摘要:

A special type of echelette grating for wavelength measurements of ultra‐short electromagnetic waves is described. The one grating may be used over the entire wavelength range from 1 to 10 cm without loss of effectiveness due to an automatically changing groove form which keeps the direction of the center of the diffraction pattern fixed. The formula for the distribution of the energy diffracted from the grating is given and found to agree with the experimental values. The magnetostatic oscillator produces a band of frequencies unless it is adjusted for the conditions at which the tube gives the maximum output, in which case no conclusions as to the width of the band could be drawn as the resolution of the spectrometer was too low.

ISSN:0021-8979    

DOI:10.1063/1.1745321

出版商:AIP    

年代:1935

数据来源: AIP