Scattering by a composite sphere with an absorbing inclusion and effectivemedium approximations

We investigate the accuracy of three effective medium approximations when a pplied to the scattering by inhomogeneous spherical particles. We compare g ross scattering properties (extinction, scattering, and absorption cross se ctions, single scattering albedo, and the asymmetry parameter) and the scat tering phase functions calculated using the effective medium approximations to those scattering properties obtained using an exact solution of the bou ndary value problem for a water droplet (sphere) containing an arbitrarily located spherical carbon inclusion. For small inclusion size parameters (x( inc) < 0.5), all effective medium approximations predict gross scattering p roperties to within 1% accuracy. As the inclusion size increases, the exten ded effective medium approximation provides greater accuracy than the other approximations. In addition, the extended effective medium approximation m ore accurately reproduces the structure of the scattering phase function. ( C) 1998 Elsevier Science B.V. All rights reserved.