WKB Approximation and Electron Tunnelling
It may not be possible to solve Schrodinger equation exactly for a variety of potentials appearing in many practical cases. Therefore, one has to rely on methods which give approximate solutions of Schrodinger equation for such potentials. One class of approximate methods is the time-independent and time-dependent perturbation theory, which we shall discuss in the next two Chapters. In this Chapter, we confine ourselves to developing the approximate method of solving one-dimensional Schrodinger equation for the case where potential energy varies slowly with position. The method we shall discuss is called the WKB approximation, after G. Wentzel, H. A. Kramers, and L. Brillouin, ...