Abstract
Expressions are given for the coherent (specular) and incoherent (diffuse) reflection and transmission of x rays by rough surfaces. In particular, the results from the distorted-wave Born approximation are critically compared with those obtained by us using the Rayleigh method. It is shown that the validity of the various expressions depends on the values of the perpendicular wave vector, the root-mean-square surface roughness, and the lateral correlation length of the roughness. The conservation of intensity in the various approximations is considered.