Moreover, numerical schemes like the propagator-matrix approach and the numerical integration of Sommerfeld integrals are also discussed. Chapter 3 covers waves in cylindrically and spherically layered media. This kind of wave problem finds applications in optics, geophysical probing, and propagation of radio waves on the earth's surface and the ionosphere. It also finds application in multilayer coatings on aircraft to reduce the radar cross-sections of aircraft. It is surprising to observe that this subject has not been developed as extensively as waves in planarly layered media.
Transient measurements are routine in radar, bioacoustic, or sonar measurements.
Chapter 4 considers the propagation of transient waves in inhomogeneous media. Chapter 5 presents the variational methods for the scalar wave equation and the electromagnetic wave equation. Such methods are often the foundation of many modern numerical methods in waves and fields, such as the finite-element method and the method of moments. Moreover, many of these numerical methods can be applied in a recipe-like manner to obtain the solution to a problem. It is still important, however, that a student understands the foundations upon which these numerical methods are based.