ABSTRACT
The absorption and spatial dispersion will be ignored and the magnetic permeability will be set at unity. Geometrical optics satisfactorily describes the field along the basic rays for smoothly inhomogeneous media. The notion of diffraction effects, generally speaking, possesses some ambiguity. In the context of practical problems the quasi-isotropic approximation equations can be solved by standard numerical methods, for example, by the Runge-Kutta method. In the case that the incident wave is an ordinary one the solution should be sought subject to the initial condition. The Landau-Zener solution described in the previous section may also be used as a basis for an asymptotic solution. The distinction is perhaps apparent only in the ability of perturbation theory applied to the full, original equations to describe the wave reflection from the stepwise change in parameters of the medium, in particular, from the region where the components of the anisotropy tensor and/or its derivatives suffer a discontinuity.
