Radiation Entropies in Diffuse Reflection and Scattering and Application to Solar Radiation

Abstract

The specific intensity of energy radiation reflected diffusely by a large sphere (or scattered by a small particle) is examined. The entropy change in diffuse reflection of radiation by the sphere (or in scattering) is given and shown to be positive. If incident radiation is black-body radiation and if the reflectivity (or the scattering ratio) is independent of frequencies of radiation, energies and entropies of diffusely reflected (or scattered) radiation can be treated as those of grey-body radiation. Effects of multiple-scattering of radiation are discussed. Results are applied to solar radiation reflected by the earth and also scattered by the atmosphere.