Reflection of Light from Semi-Infinite Absorbing Turbid Media. Part 1: Spherical Albedo

摘要

The purpose of this article is to study the accuracy of a number of simple approximate equations for the spherical albedo r (or the hemispherical reflectance under diffuse illumination conditions) of semi-infinite light scattering absorbing media, using numerical solutions of the nonlinear integral equation for the reflection function of a semi-infinite turbid medium, as formulated by V. A. Ambartsum-ian. We find that the van de Hulst approximation provides the most accurate approximation for the diffuse reflectance r under diffuse illumination conditions. The value of r depends almost exclusively on the value of the similarity parameter s = ((1 - ω_0)(1 - gω_0)~(-1))~(1/2), where ω_0 is the single scattering albedo and g is the asymmetry parameter. A simple approach to derive the normalized absorption spectra of paniculate matter from reflectance measurements is proposed.