We have calculated numerically the scattering of a scalar beam incident normally on a large-amplitude, large-rms-slope, two-dimensonal, randomly rough, hard wall (Dirichlet boundary condition). Our result is equivalent to a fourth-order Kirchhoff approximation, and displays a well-defined peak in the retroreflection direction in the angular dependence of the intensity of the waves scattered incoherently.

• Received 12 August 1991

DOI:https://doi.org/10.1103/PhysRevB.45.3936