Coherent and incoherent backscattering by a single large particle of irregular shape

Intensity of light scattered by a large randomly oriented particle of irregular faceted shape at the backscattering cone of [170°, 180°] is calculated using the physical-optics approximation. It is shown that the backscattered light for a single large particle of irregular shape is split into the coherent and incoherent parts similarly to the phenomena well-known for multiple scattering media. For the model of irregular faceted particles assumed in the paper, the coherent part creates the coherent backscattering peak whose angular width is equal approximately to the ratio of wavelength/(particle size). The incoherent part approaches to the smoothed geometric-optics solution. For other models of faceted particles where the dihedral angle of 90° among the facets is essential, the incoherent part creates as well the incoherent backscattering peak with another angular width.