  Multiple scattering of polarised electromagnetic waves in diffusive media is
investigated by means of radiative transfer theory. The method becomes exact in
several situations of interest, such as a thick-slab experiment (slab thickness
L >> mean free path $\ell >> wavelength \lambda)$. The present study is
restricted to Rayleigh scattering. It incorporates in a natural way the
dependence on the incident and detected polarisations, and takes full account
of the internal reflections at the boundaries of the sample, due to the
possible mismatch between the mean optical index n of the medium and that n_1
of the surroundings. Quantities of interest, such as the polarisation-dependent
angle-resolved mean diffuse intensity in reflection and in transmission and the
shape of the cone of enhanced backscattering, are predicted in terms of
solutions to Schwarzschild-Milne equations. The latter are obtained
analytically both in the absence of internal reflections and in the regime of a
large index mismatch.
