Diffuse Reflection and Transmission of Light by Atmospheres

Abstract

From now on we commence a systematical study of radiation fields in an inhomogeneous atmosphere whose optical properties depend on only one spatial coordinate, namely, optical depth. In the beginning we will consider the simpler problem of how to determine the transmission and reflection coefficients for a plane layer of inhomogeneous atmosphere. So, in other words, we will be interested in the intensity of the radiation diffusely transmitted and reflected by the medium (see Sect. 1.9). This problem is one of the most important in astrophysics. Observing celestial bodies, we mostly deal with either the intensity of the radiation diffusely reflected by their surface (planets, gaseous and dust nebula) or the intensity of the radiation that diffuses through their atmosphere from a source in the deep layers of the medium (stars). For a homogeneous atmosphere, both problems are known to be closely connected (see Sect. 3.3). It is important to note here that the problem of determination of the reflection and transmission coefficients can be solved without the main problem (i.e., the determination of the radiation field in the atmosphere) being solved.