Lichtenecker's equation: applicability and limitations

Lichtenecker's equation for the effective dielectric function is considered with the help of spectral representation. The spectral density function of resonances is determined and its behavior is analyzed. This analysis is carried out at different values of a parameter specifying the composite topology. It is shown that Lichtenecker's equation describes a specific composite topology only. It is not reduced to the Bruggeman topology but may be represented as a spheroid system.