Depolarization of light backscattered by randomly oriented nonspherical particles

Abstract

We derive theoretically and validate numerically general relationships for the elements of the backscattering matrix and for the linear, δ_L, and circular, δ_C, backscattering depolarization ratios for nonspherical particles in random orientation. For the practically important case of randomly oriented particles with a plane of symmetry or particles and their mirror particles occurring in equal numbers and in random orientation, δ_C = 2δ_L/(1 − δ_L). Extensive T-matrix computations for randomly oriented spheroids demonstrate that, although both δ_L and δ_C are indicators of particle nonsphericity, they cannot be considered a universal measure of the departure of particle shape from that of a sphere and have no simple dependence on particle size and refractive index.