Condensed Matter Physics - Band Theory of Solids : The Kronig-Penney Model - 02

This is the second part of the lecture on K-P Model. The result obtained in the first part of this lecture has been discussed here in very detail. It is seen that when the parameter P is large then the allowed bands are narrow and the forbidden bands wide. In the extreme condition when P is infinitely large then the allowed bands are infinitely narrow and the energy spectrum takes the shape of a line spectrum. If P=0 then the electrons behave as a completely free electron. The occurrence of gaps can be understood in terms of Bragg reflection of de Broglie waves associated with the electron moving through the lattice.