Light Scattering in Stretched Rubber

Abstract

Abstract It is already known that when pure rubber is stretched in one direction it acquires a lustre. This means that light falling upon it is scattered with appreciably different intensities at various angles to the direction in which the rubber is stretched. In view of this and in connection with earlier experiments, a study of the scattering of visible light by stretched rubber was undertaken and the first results are reported in a brief way in the present paper. First of all, however, it is well to describe the experimental apparatus and technique which were used. A practically parallel, sharp beam of light was produced, the direction of which may be represented by the X-axis of a system of right-angle coordinates. The rubber test-specimen, in the form of a strip, was placed in such a position in the path of this beam of light that it was illuminated by the beam at right angles to its surface. In other words, the specimen lay in the YZ plane of the coördinate system and by means of a special device it could be stretched in the Z direction. At a suitable distance behind the test-specimen a smooth, transparent paper screen was placed, likewise at right angles to the direction of the beam of light. The distribution of the scattered light around the bright spot formed by the transmitted light could be observed by eye and could be photographed by a camera. Samples of rubber as nearly pure as possible and containing no fillers were examined, including not only films prepared from pure unvulcanized and partially vulcanized latex, but also strips prepared from commercial sheets of “patent rubber” and from Para rubber.