Abstract
We discuss the theory of diffraction as a singular perturbation problem. Due to the presence of two different lengths—the wavelength and the characteristic geometric length of the scatterer—there exists no uniformly valid series expansion of the scattered field in the entire region. As such, two different expansions are needed; one of them is valid in the near region and the other in the far region. These two series are then matched in an appropriate fashion. It emerges from this analysis that first two terms of the required asymptotic expansion can be obtained by solving two simple problems of the potential theory.

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