This book is aimed at studying the scattering of monochromatic radiation in plane inhomogeneous media. We are dealing with the media whose optical properties depend on a single spatial coordinate, namely of a depth. The most widely known books on radiation transfer, for instance 1. S. Chandrasekhar, Radiative Transfer, Oxford, Clarendon Press, 1950, (RT), 2. V. V. Sobolev, Light Scattering in Planetary Atmospheres, New York, Pergamon Press, 1975, (LSPA), 3. H. C. van de Hulst, Multiple Light Scattering. Tables, Formulas and - plications. Vol. 1,2, New York, Academic Press, 1980, (MLS), treat mainly the homogeneous atmospheres. However, as known, the actual atmospheres of stars and planets, basins of water, and other artificial and nat ural media are not homogeneous. This book deals with the model of vertically inhomogeneous atmosphere, which is closer to reality than the homogeneous models. This book is close to the aforementioned monographs in its scope of prob lems and style. Therefore, I guess that a preliminary knowledge of the con tents of these books, particularly of the book by Sobolev, would facilitate the readers' task substantially. On the other hand, all concepts, problems, and equations used in this book are considered in full in Chap. 1. So, it will be possible for those readers who do not possess the above knowledge to understand this book. A general idea about the content of the book can be gained from both the Introduction and the Table of Contents.