Spheres

Scattering of a plane electromagnetic wave by a spherical object is perhaps the important canonical problem in electromagnetic scattering theory. The sphere serves as a model of a compact smooth scatterer and is one of only two compact geometries for which Maxwell's equations can be solved in an explicit form. An exact solution is available not only for perfectly electrically conducting (PEC) but also for material, homogeneous or radially stratified, magneto‐dielectric spheres. This chapter addresses the physical interpretation of scattering from spheres, depending on the electrical size and the degree of absorption in the material of the sphere. It applies the general solution for the far scattered field to the particular cases of two concentric spheres and their variants, including PEC, impedance, and core‐shell spheres, and describes the most important features of low‐ and high‐frequency scattering from these structures.