PROPAGATION OF CLASSICAL WAVES IN RANDOM-MEDIA

An extension of the well-known coherent-potential-approximation is developed for the study of various properties of random arrangements of spherical dielectric scatterers. Some of the short-range order is taken into account by considering a coated sphere as the basic scattering unit. A generalization of the energy-transport velocity is obtained. The validity of our approach is checked by comparison with experimental results, as well as with numerical calculations. Results for the long-wavelength effective dielectric constant, phase velocity, energy-transport velocity, mean free path, and diffusion coefficient are presented and compared with experiments on scattering from dielectric spheres. In addition, our findings suggest that the positions of the band gaps in periodic dielectric structures are closely related with the range of localized states in random dielectric media.