Polarization and Visibility (First Report)

Abstract

In order to study the polarization of the light from the sky, cloud-layers, sea surface and skirts of mountains, and to improve the visibility (contrast of objects) by using Polaroid, we did some fundamental observations on Mt. Fuji in July, 1944.
The Principal part of our instrument is composed of twp cylindrical tubes; the former half, having Polaroid plate at its end, can be rotated around its center oxis, contacting with the rear half. Matsuda's photocell set at the end of the rear half will change the intensity of the polarized light into photo-current which can be measured by Siemens photometer. By the aid of a tripodal, the tube can be pointed towards any direction arbitrarily. The result can be summarized as follows:
(1) The polarization of light from the sea surface, skirts of mountains and cloudlayers depends mainly upon light-scattering caused by the air between objects and observer not receiving the reflected light from the objects themselves. This polarization is in accordance with the well-known facts of polarization of the sky light; except the fact that the degree of polarization is smaller than the case of sky light.
(2) Moreover, we observed the polarization of the light from white rainbow, sky in moonlight night, corona etc. White rainbow caused by cloud-layers showed strong polarization and was measured quantitatively.
(3) As we can expect from the idea of Koschmieder's contrast, in cases of (i) comparing two objects, polarization of the darker one is stronger, and (ii) if the brightness is the same, either one can be stronger, and we can improve the vis_??_bility by using polaroid plate. This effect is striking, especially in cloud observation at twilight or moonlight night.