Scattering of polarised light by colloids containing anisotropic particles

Abstract

It is only recently that the theoretical significance of the elliptic polarisation of light scattered by colloids containing particles of large size has been pointed out and an analysis made of the theoretical conclusions regarding ellipticity from Mie's theory for spherical particles. The earlier qualitative measurements on ellipticity of the scattered light have been explained on the basis of these new ideas and the implications of Mie's theory brought out more clearly. New experiments have been devised and used for measuring the constant phase difference δ that exists between the vertical and horizontal components of the transversely scattered light when the incident light is polarised in any azimuth. Measurements have been made both for systems of spherical particles and anisotropic particles. It is found that even in the case of large anisotropic particles δ is a constant. It follows therefore, that in the most general case of large anisotropic colloidal particles the polarised scattering due to finite size is elliptic in nature and is superposed on the depolarised part due to anisotropy.