The Use of Ray Methods and First Order Diffraction Corrections

摘要

In many wave problems, ray methods are convenient and accurate. Exact in the limit of high frequency, and employing simple formulae, these methods lose utility at low frequencies or because of inadequate numerical schemes for interpreting them. Correction terms are given which permit an extension of ray methods to lower frequencies (and at the same time providing an estimation of the validity of the high frequency limit). Some useful formulae and numerical schemes for ray tracing and the quantitative evaluation of refraction (spreading) and interference are given.