Conditions of applicability of the single-scattering approximation.

We employ the numerically exact superposition T-matrix method to perform extensive computations of electromagnetic scattering by small volume elements filled with 8 randomly distributed wavelength-sized spherical particles. The results of these computations are used to examine quantitatively the conditions of applicability of the single-scattering approximation (SSA). We show that one may need large inter-particle distances and low packing densities in order to make the SSA sufficiently accurate.