Test of the Representative Layer Theory of Diffuse Reflectance Using Plane Parallel Samples

Abstract

Equations of Benford used in the Representative Layer Theory are able to describe spectroscopic remission from layered plane parallel samples (plastic sheets) quite effectively. Losses due to reflection directly back in the direction of the incident beam are a major cause of discrepancies. Non-compositional variation and experimental errors tended to produce linear changes in the absorption coefficient, with the remission coefficient being more drastically affected. The remission coefficients obtained experimentally, in general, vary inversely to the absorption coefficient, although, as predicted by theory, front surface reflectance causes a direct variation. In transflectance, the log(1/ R) spectrum of the thinnest samples is the one that is most like the absorption coefficient curve, but the shape of the Kubelka–Munk (absorption/remission) spectra are less affected by sample thickness, especially in the absence of surface reflection.