Note on the scattering of waves by rough surfaces

A calculation of back scattering from a rough surface using Huygen's principle is carried out along the lines introduced by Davies. Davies original equation is extended to include a contribution from the component of the surface normal which is parallel to the average surface. The effect of this component is to multiply the usual expression for incoherent backscatter by a factor of
1/ \cos^{4} \Psi
where
\Psi
is the angle between the radar line of sight and the normal to the average surface.