title: Radiative transfer in a turbid medium with a varying refractive index: comment.
abstract: In the literature one can encounter at least two different radiative transfer equations for media with spatially varying refractive indices. These are the results of Ferwerda [J. Opt. A Pure Appl. Opt. 1, L1 (1999)] and Tualle and Tinet [Opt. Commun. 228, 33 (2003)]. Accordingly, two different diffusion approximations are derived from these two radiative transfer equations. I reconsider the derivation of the radiative transfer equation in a medium with an inhomogeneous refractive index and confirm the result of Tualle and Tinet. In the diffusion approximation, a simple analytical solution has been found for the steady-state illumination of a non-absorbing turbid medium with a varying refractive index.
authors.affiliation: School of Engineering, South Bank University, London SE1 0AA, UK. shendem@lsbu.ac.uk
authors.forename: Margarita L
authors.initials: ML
authors.lastname: Shendeleva