Angular distribution of diffusely transmitted light

The angular dependence of light diffusely transmitted through an opaque medium is shown to depend directly on the reflective nature of the sample boundary, independent of scattering anisotropy. Experimental data are presented for glass frits and for liquid samples, such as colloidal suspensions and aqueous foams, contained in glass cells and placed in either air, water, or glycerin baths. Results compare well with a simple theoretical prediction based on the diffusion approximation and also with random walk simulations. The importance of this work is not only in providing a simple quantitative explanation of a complex transport problem, but in establishing the proper treatment of boundary conditions for diffusion theory analyses of multiple light scattering experiments.