Depolarization of light in small-angle multiple scattering in random media

The decay of light linear polarization by multiple scattering in a random medium with large-scale inhomogeneities is considered. The small-angle vector transport equation is derived. The Stokes parameters in the small-angle diffusion approximation are calculated. It is shown that there is a qualitative difference in decay mechanisms for circular and linear polarization: the circular polarization decays much slower than the linear polarization.