  In this paper, we present an approximate expression for determining the
effective permittivity describing the coherent propagation of an
electromagnetic wave in random media. Under the Quasicrystalline Coherent
Potential Approximation (QC-CPA), it is known that multiple scattering theory
provided an expression for this effective permittivity. The numerical
evaluation of this one is, however, a challenging problem. To find a tractable
expression, we add some new approximations to the (QC-CPA) approach. As a
result, we obtained an expression for the effective permittivity which
contained at the same time the Maxwell-Garnett formula in the low frequency
limit, and the Keller formula, which has been recently proved to be in good
agreement for particles exceeding the wavelength.
