Ray scattering model for spherical transparent particles.

We propose a model for the reflectance of a particle medium made of identical, large, spherical, and absorbing particles in a clear binder. A 3D geometrical description of light scattering is developed by relying on the laws of geometrical optics. The amount of light backscattered by a single particle is determined as a function of its absorbance and refractive index. Then, we consider a set of coplanar particles, called a particle sublayer, whose reflectance and transmittance are functions of the particle backscattering ratio and the particle concentration. The reflectance of an infinite particle medium is derived from a description of multiple reflections and transmissions between many superposed particle sublayers. When the binder has a refractive index different from that of air, the medium's reflectance factor accounts for the multiple reflections occurring beneath the air-binder interface as well as for the measuring geometry. The influences of various parameters, such as the refractive indices and the particle absorption coefficient, are examined.