The method of a previous paper is applied to the reflection and refraction of a weak spherical or cylindrical shock wave at a plane interface and by a plane slab. The method is also extended to apply to the diffracted wave which appears in these problems whenever total reflection occurs. From the results the leading terms in the asymptotic expansions for high frequency of the fields produced by periodic point or line sources over a plane interface are also obtained. These terms, which apply to electromagnetic as well as acoustic fields, are in exact agreement with results previously obtained by much more complicated methods.