Phương tiện truyền thông tự nhiên - không khí, đất, và những người khác - có thể được nghĩa vụ phải được đồng nhất trong khu vực giới hạn của không gian. Trong thực tế, permittivity của các phương tiện truyền thông là một chức năng của tọa độ, trong thuật ngữ chung, thời gian, đó là bỏ qua, như một quy luật, bởi vì trì trệ so sánh quá trình tự nhiên. Như thường lệ, thời gian cần thiết cho truyền sóng điện từ trong môi trường tự nhiên là ít hơn nhiều so với thời gian điển hình. | 3 Wave Propagation in Plane-Layered Media REFLECTION AND REFRACTION OF PLANE WAVES AT THE BORDER OF TWO MEDIA Natural media the atmosphere earth and others can be supposed to be homogeneous only within bounded area of space. In reality the permittivity of these media is a function of the coordinates and in general terms time which is ignored as a rule because of the comparative sluggishness of natural processes. As usual the time required for electromagnetic wave propagation in a natural medium is much less than typical periods of medium property changes. In the first approximation natural media can be considered to be plane layered that is their permittivity changes in only one direction. If a Cartesian coordinates system is chosen in such a way that one of the coordinates for example z coincides with this direction then we may say that permittivity depends on this coordinate only. For the atmosphere of Earth a concept of spherical-layered media would be more correct and this idea is considered in the following chapters however we should point out that the curvature radius of media layers of the Earth is so large that the concept of plane stratification is sufficient in many cases. In this chapter we will study only plane wave propagation in plane-layered media. We will assume waves as the plane only conventional because surfaces with constant phase and constant amplitude are not planes in the cases of wave propagation direction inclined to the layers. On the whole wave parameters cannot depend on only one particular Cartesian coordinate in all cases. In most of the cases that we will consider here media parameters change little compared to wavelength therefore surfaces of equal phase or amplitude have sufficiently large curvature radii to be considered locally plane. It is quite acceptable to talk about plane waves in these terms. In some situations medium properties can be changed sharply and on a wavelength scale however regions of such great change are .
