Rayleigh scattering in an optically anisotropic medium

When a plane-polarized light beam is passed through an anisotropic medium, the extraordinary ray can become retarded or advanced relative to the ordinary ray. This leads to a periodic longitudinal extinction of (λ/Δn) along the light path which provides a quick accurate visual method for determining the birefringence of a material which is both transparent and a good scatterer of light. © 1967 The American Institute of Physics.