Small-angle scattering by rough and fractal surfaces

Small-angle scattering due to surfaces occurs in two general situations. The first is the scattering from a single oriented surface and the second is the scattering from two-phase composites or porous media with randomly oriented internal surfaces. The scattering theory for rough and fractal surfaces in both situations is summarized, and the effects of a density gradient at the surface and strong scatterers absorbed on the surface are discussed.