Figure 4

Steady-state spatially resolved reflectance from the three-layered scattering medium with an absorption coefficient of the lower semi-infinite layer of \({\mu }_{a}^{\mathrm{(3)}}=0.02\,{{\rm{mm}}}^{-1}\) and a refractive index of n _m  = 1.4 due to a perpendicularly incident Gaussian beam with a beam radius of ρ _w  = 0.5 mm. The refractive index of the surrounding medium is n ₀ = 1.0. For N ≥ 9, the Monte Carlo simulation and the P _N solution agree well. For the Monte Carlo simulation, 10¹¹ Photons were calculated.