Theory of absorbers in scattering

The effect of absorbers on scattering from complex shapes is considered, wherein, unlike previous work on the subject, the diffracted field is taken into account. For a general class of scattering bodies two new theorems are introduced which give conditions under which the back-scattered field for incident radiation is identically zero. High-frequency scattering from any smooth convex body is examined. The conditions given in the theorems are then used to determine their effect on the creeping waves. It is shown that the creeping waves suffer much greater attenuation than they would if the body were a perfectly conducting surface. The particular case for nose-on back-scattering from a body of revolution is considered, for which case the creeping wave contribution to the back-scattered field is identically zero due to phase cancellation. It is then shown that absorbers with highly refractive lossy characteristics will reduce the back-scattered cross section for smooth convex bodies in the resonance region.