An equipment for measuring the reflection spectrum of a pearl was constructed from theoretical consideration. The equipment consists of a spherical dome of radius 60mm, in which a pearl is held at the center of the dome and a detector for measuring the pearl reflection spectrum. By using the equipment, relative reflection spectra of silver, cream and black pearls (radius 4mm) were measured. The measured spectra were confirmed to be appropriate comparing with the already published experimental data. Although an error of the spectrum owing to the deviation of the pearl holding-position was also checked, it was fairly small; such a property is of strong merit in the case of high speed-measurements.
Current oscillation phenomenon in a semiconductor bar with a partially narrow cross-section (hereafter, this narrow region is referred to as notch) was experimentally studied. The current-voltage characteristic shows a low frequency current oscillation following a sublinear characteristic. Distributions of electric field and carrier concentration in the sample were measured under light illumination and compared with the case in darkness. Dependence of the drift velocity of injected holes on the applied field was measured to clarify the cause of the sublinear characteristic. It was confirmed that a high electric field region which causes the sublinear characteristic exists near the notch, and that a narrow region near the notch shows a negative resistance characteristic. It could be speculated that a simultaneous appear-ance of sublinear and negative resistance characteristics is required for the occurrence of current oscillation.
Electron microscopical observation on thin Ge and Bi films vacuum-deposited on the basal or the lateral plane of stearic acid crystals has revealed a remarkable difference in the microstructure between the deposited films on these two planes ; namely, a discontinuous island structure on the basal plane and a continuous layer structure on the lateral plane. This is available for the surface identification of the surfaces of vapor-grown stearic acid particles.
By means of a differential-type laser velocimeter using a spatial grating filter, the velocity of water flowing in a small glass tube with a diameter of 700 μmø is successfully measured. This velocimeter is so simple, both in its optical system and its operation of measurements, that it is not affected by small vibrations in comparison with a laser Doppler velocimeter. The experimental results show that the present velocimeter with a differential detection system is suitable and practical for measurements of flow velocity and its spatial distribution in a microscopic area where an electrical high-pass filter is not available for removing the pedestal component of output signals.