Determination of absorption and scattering coefficients for nonhomogeneous media. 1: theory.

Equations are derived to determine the diffuse reflectance and transmittance of inhomogeneous materials. The equations are valid for collimated incident radiation for any angle of incidence. The effects of boundary reflectance and anisotropic scattering are included. The equations are derived from the equation of radiative transport, using the Schuster-Schwartzchild approximation. They are sufficiently simple to be used for spectroscopic determination of the absorption and scattering coefficients. Numerical comparison with more exact solutions of the equation of radiative transfer show very good agreement for all cases except for reflectance in the highly anisotropic case, where agreement is only fair.