TABLE OF CONTENTS Aerosol light scattering plays a major role in the design of aerosol measurement systems (discussed in the next chapter) and radiation transfer through the atmosphere. There are also technological applications in combustion and production of powdered materials. This chapter provides an introduction to the subject.
In broad outline, the problem of light scattering by clouds of small particles can be formulated as follows: Scattering by an individual particle depends on its size, refractive index and shape, and the wavelength of the incident light. There is an extensive literature on the optical properties of single particles (van de Hulst, 1957; Kerker, 1969; Bohren and Huffman, 1983) to which we refer without derivation. The total light scattered from a collimated light beam is obtained by summing the scattering over particles of all sizes and refractive indices, subject to certain limitations discussed in this chapter. In practice, light sources and sinks are distributed in space in a complex way; the radiation intensity at any point is determined by the arrangement of the sources and sinks, the spatial distribution of the aerosol, and its size distribution and composition. In laboratory studies, it is possible to control these variables; and for certain relatively simple configurations (e.g., single scattering and collimated light sources), good agreement can be obtained between theory and experiment. Applications to industrial process gases and to radiation transfer through planetary atmospheres are more complicated. They can sometimes be analyzed using the equation of radiative transfer; an application to atmospheric visibility is discussed.
