In double-beam spectrometer observation using optical null method, it is necessary to move the optical wedge in one direction or in the other to balance the intensities of the sample and reference beams. To facilitate this operation, a tuning fork with a small mirror is used as a chopper, and the output power of the tuning fork oscillator is used as one of the two inputs of the servomotor which drives the optical wedge. The other input of the servomotor is supplied by the amplified power of the detector, whose phase is adjusted to be either 90° ahead or behind of that of the first input depending upon which of the two beams is stronger. Using this system with a PbS photoconductive cell, near-infrared absorption spectrum of liquid chloroform is recorded.
Applying Nomura's results on the diffraction of electromagnetic waves by a semi-infinite perfectly conducting sheet, formulas on diffraction by an infinitely long and perfectly con-ducting ribbon sheet are deduced. Directional characteristics of a doublet antenna with such reflector are calculated by the formulas and compared with those of a doublet antenna with an infinitely extended and perfectly conducting reflector. Corresponding characteristics of these two cases are different, especially in the H-plane. The difference is due to the effects of the two edges of the reflector. Consequently, it will be seen that, for a rectangular re-flector used as radiator of micro-waves, effects of four edges must be taken into account by deducing formulas similar to those shown in this paper.
Barkas' analysis (Proc. Phys. Soc. 51, 274, (1939)), in which the scattered light is decom-posed into specular and diffuse components and is treated geometrically, is tried on the light scattered by the surface of paper. Several kinds of printing paper and filter paper, white and dyed by diluted red ink, are used for experiment. Results obtained are as follows: 1. For highly glossy papers, the analysis is not applicable as it gives a negative value for the diffuse component. 2. Although the analysis is formally admissible for less glossy papers, there is no sound physical ground to designate two independent components, specular and diffuse, as the former varies considerably with the power of absorption of the paper. 3. That the analysis does, not explain the diffuse reflection is due to the fact that the so-called specular reflection does not follow Fresnell's formula.
On the basis of the conclusion already reported1), original Hardy-type spectrophotometer has been modified by adding special optical system, which permitted color-measuring of small spherical objects to the accuracy of 1 NBS. With this new instrument it is possible to dis-criminate the color-differences of pearls to the extent sufficient for the purpose. The difference between the values of reflectances R_??_ and R_??_, of the same pearl, measured on MgO-Background, and on 5% neutral Reflector-Background respectively, is found to play the main role on the human impression of both nuance and color of the pearl. The comparison between the colorimetric data obtained and those by visual colorimeter4) indicates that, even though their colorimetric conditions are essentially different, the corres-pondency between them is sufficiently good as a whole when pearls are measured on MgO-Background.
This apparatus has been deviced for continuous recording of gas content ratio using interferometric gas analyzer. Interference fringes are focused through two reflecting prisms and a cylindrical lens on to photographic paper moving with a constant speed. Due to the change of gas composition, the fringes move, and are recorded on the photo-graphic paper, which, after exposed, passes through developing, fixing and washing baths. From the fringe shift on the paper, volume percentage of the gas is measured. Even the slightest change of pressure in gas chamber results in large error. To avoid the pressure change during gas sampling, a device is used so that the gas is introduced into the gas chamber intermittently and is recorded only when pressure is balanced. With this instrument, a variation of 5×10-7, in refractive index or 0.1% CO2, in air can be detected. This instrument can be used in coal mines and various chemical factories for the pre-vention of danger and in theaters and public halls for sanitary purposes.