Light scattering at the boundary between two media

Coefficients of diffuse reflection and transmission of light by smooth Fresnel boundaries of an optically thick layer illuminated by scattered radiation are calculated. Consideration is given to the absorption effect on angular diagrams of light at the boundaries. An analysis is made of asymptotic equations of radiation transfer in a medium with reflecting boundaries, and the range of their applicability is studied. Using methods of geometric optics, coefficients of reflection of directional and diffuse radiation from a rough surface are studied. The results can find use in various areas of science and technology, specifically, in optical diagnostics of biological tissues.