Radiative heat transfer in a participating finite slab medium with variable refractive index is considered. The medium is subjected to externally incident radiation and the medium boundaries are considered to have diffuse reflectivities. The solution of the source-free problem is obtained by using Pomraning-Eddington method. This method transforms the radiative transfer intergo-differential equation into two second order differential equations which have analytical solution in terms of the modified Bessel functions. Numerical results are calculated for the reflectivity and transmissivity at the medium boundaries with varying the single scattering albedo and the refractive index of the medium. Comparing the calculated results with the published data shows good agreement. (C) 2013 Elsevier Ltd, All rights reserved.