The determination of light absorption in diffusing materials by a photon diffusion model

The mechanism of light reflection from diffusing materials is considered as a photon diffusion process. Equations from neutron diffusion theory are adapted to give reflection factors in terms of the scattering and absorption cross sections of the diffusing material. Measurements of the reflection spectra from blue and green ground glass are used to calculate the absorption spectra of the original glass using diffusion theory. Good agreement is obtained between the absorption spectra measured by transmission on the original glass and that calculated from the reflectance spectra of the ground glass. Comparison with the Kubelka and Munk coefficients of scatter and absorption calculated from the same data shows that diffusion theory gives a more accurate description of the absorption process. The variation of the scattering cross section and scattering coefficient of Kubelka and Munk with wavelength is similar for the ground glasses considered.