50 years with J. B. Keller´s Geometrical Theory of Diffraction in Denmark - Revisiting the Theory: Impedance Half-Plane Diffraction Coefficients

In the introduction, Danish contributions to J. B. Keller´s Geometrical Theory of Diffraction are surveyed. The edge diffraction coefficient in the case of scattering by a half-plane with an impedance surface is then analyzed. In short-wavelength scattering theory, the amplitudes of the incident and the reflected rays are of the same order of magnitude. The consequence of this point of view for the structure of the diffraction coefficient is investigated.