Physical Optics Solution Research Articles

A modified geometrical optics method for scattering by dielectric bodies

A method based on ray optics is developed for calculating the scattering from dielectric bodies. The fields of geometrical optics are used except for two types of rays where the fields must be corrected from physical optics solutions. The customary advantages of ray techniques are realized, namely, a simplicity in the resulting formulas, a ready interpretation of the scattering mechanism and the possibility of extension to a wider class of problems through the inclusion of additional rays. The method has been applied to several lossless dielectric shapes: the circular cylinder, the sphere, the prolate spheroid and to a lossy dielectric shell. The relative dielectric constants considered range from 0.25 to 1.80, except in the case of the shell. The calculated results are compared with those obtained from boundary value solutions, with the exception of the spheroid where measured values are used. Good results are obtained for all sizes considered except those which are very small and behave as Rayleigh scatterers. The failure in the region of Rayleigh scattering is to be expected. Thus, for the class of dielectric scatterers treated here there is no region of scattering resonance corresponding to that of similar metallic shapes where the geometrical optics solution is no longer valid.

On scattering by large conducting bodies

Two sets of sources, equivalent in sense that they produce same field as does an illuminated conductor, are discussed. Both representations are suggestive of approximation. Crude approximations are made, yielding what are called the physical optics solution, and image induction solution. It is shown that these two solutions are reciprocal to each other. This means that, given a source and an observer, solution by one method is equal to solution by other method with source and observe interchanged. Both solutions are amenable to further refinement if more accurate solutions are desired.