The diffusion approximation is widely invoked to model the propagation of light in turbid media. When absorption is not weak in comparison with scattering, there is currently a controversy as to if, and how, the diffusion coefficient depends on absorption. Here it is shown that better agreement with random walk simulation is obtained if the photon-diffusion coefficient is taken as D=c/(3µ<sub>s</sub><sup>′</sup>+µ<sub>a</sub>) . One can reconcile this result with recent work advocating D=c/3µ<sub>s</sub><sup>′</sup> by noting that the diffusion equation must be correspondingly changed to a telegrapher’s equation.
© 1998 Optical Society of AmericaPDF Article