Effective dielectric constant of a medium with spherical inclusions

The Maxwell-Garnett theory is frequently used to predict the effective, or the average, dielectric constant of a mixture composed of spherical inclusions embedded in a host medium. This effective medium theory assumes that the volume fraction occupied by the spherical inclusions is small and that the size of the inclusions is small compared to the wavelength. Experiments using controlled samples have shown that the Maxwell-Garnett theory is applicable up to an inclusion volume fracton of 0.2. At higher volume fractions, the effective dielectric constant appears to be dependent on the inclusion sizes