Basic Notions in Acoustic and Electromagnetic Diffraction Problems

In two-dimensional problems, the physical theory of diffraction (PTD) is valid for both electromagnetic and acoustic waves. This chapter presents the theoretical fundamentals for acoustic and electromagnetic waves. To complete formulation of the diffraction problem and ensure the uniqueness of its solution, the wave equation and boundary conditions are supplemented by the Sommerfeld radiation condition for the scattered field. The high-frequency physical optics (PO) approach is widely used in acoustic and electromagnetic diffraction problems. Among the properties of the shadow radiation, the most significant are the shadow contour theorem and the total power of shadow radiation, which are verified for acoustic and electromagnetic waves, in the chapter. Taking into account the diffraction and nonuniform components of surface fields, PTD overcomes the PO shortcomings and provides more accurate asymptotic results for high-frequency scattered fields.