The light scattered by gases: its polarisation and intensity

Abstract

The present investigation is a development in various directions of that described in ‘Proc. Roy. Soc.,’ A, vol. 94, p. 453 (1918). It is there shown that the light scattered by air and other gases in the direction perpendicular to the beam is almost completely polarised. It is of importance to determine whether or not the polarisation of the scattered light at right angles to the beam is absolutely complete. Sky light is by no means completely polarised, but in that case the incident light is not all in one direction: for, besides direct sunlight, light from other parts of the sky and from the earth’s surface contributes to the scattering from any given element of volume. The question is whether, apart from these complications, the polarisation would be complete. This cannot be decided by observations on the sky, but the laboratory methods now described allow of its investigation, not only in air, but in other gases also.