Introduction

Wave propagation is a salient feature of many phenomena occurring in continuum physics. In most cases (short wavelength limit) an adeguate description can be obtained in terms of rays and propagation laws (for amplitude and polarization) along rays. The essence of the method lies in the derivation of ray equations and propagation laws from the field equations utilizing appropriate asymptotic expasions (in terms of the wavelength). The fundamental problems, in nonlinear wave propagation which will be tackled by the ray method, are shock wave propagation, derivation of model equations and interaction of waves. The chapter also presents an overview of the key concepts discussed in this book.