ANGULAR-DISTRIBUTION OF DIFFUSELY BACKSCATTERED LIGHT

We demonstrate that the angular distribution of light diffusely backsc attered from an opaque slab depends not only on sample boundary reflec tivity but also, in contrast to previous results for diffusely transmi tted light, on the anisotropy of the scattering events. This influence of scattering anisotropy is modeled within diffusion theory by a disc ontinuity in the photon concentration at the source point that is prop ortional to the average cosine of the scattering angle. The resulting predictions are compared with random walk simulations and with measure ments of transmitted and backscattered intensity versus angle for glas s frits and aqueous suspensions of polystyrene spheres held in air or immersed in a water bath. Predicted distributions capture the features of experimental and simulation data to within 1% for the best case of high reflectivity and weak anisotropy and to within 10% for the worst case of low reflectivity and strong anisotropy. (C) 1997 Optical Soci ety of America.