Diffusion of light in turbid media with internal reflections

We relate the Kubelka-Munk equations for description of intensity transfer light in turbid media to a one-dimensional diffusion equation, which is obtained by averaging three-dimensional equation over lateral directions. This enables us identify uniquely parameters and derive expressions diffuse reflection transmission coefficients including effect internal reflections. Without reflections we recover formulae these coefficients. show that are proper radiative-transfer problem.