We use the radiative transfer equation to study the multiple scattering undergone by a laser beam propagating through a turbid medium. During the propagation, we view the beam as first scattering into a narrow forward cone, and then into a diffuse pattern. To describe this process, we propose a systematic and practical method to combine the small angle approximation with the diffusion approximation. The method works when the scattering cross-section describing scattering from aerosols can be written as the sum of a gaussian sigma/sub s/ to describe scattering into small angles, and a term sigma/sub d/, that can be represented by the first two terms of a Legendre expansion to describe scattering into large/diffuse angles. We use a Green's function formalism to perform partial resummations and set up a hierarchy of approximations in the form of coupled radiative transfer equations to describe the scattering of radiation from small angles into large angles. The adjoint operator formalism then provides a simple way to obtain the net flux received by an open detector at any given point. Our approximations may be described rigorously as a power series expansion in sigma/sup 0//sub d//sigma/sup 0//sub s/, the ratio of the diffusion scattering cross-section to …

Document issued by the Office of the Attorney General of Texas in Austin, Texas, providing an interpretation of Texas law. It provides the opinion of the Texas Attorney General, Jim Mattox, regarding a legal question submitted for clarification; Whether a county clerk may deliver the services of his office on credit.