Absorption spectrum of metal-coated particles

A theory for the absorption spectrum of light by a metal-coated insulating particle suspended in another insulating medium is described. Electromagnetism of dielectric media is employed to evaluate the strength of a local electric field and electric polarizability is evaluated by using the Kubo formula. The computed absorbance spectrum agrees well with that experimentally observed. Dependence of the absorbance on various combinations of physical parameters for each substance is also presented.