Figure 1: Semi-infinite turbid medium geometry.
From: Photon diffusion near the point-of-entry in anisotropically scattering turbid media
The medium is illuminated with a narrow collimated beam. In addition to unscattered photons, low-angle-scattered photons are also shown. Any point along the beam can be a source of a single large-angle turn, which is followed by low-angle-scattered photons propagating towards the surface. The large angle turn is described by the phase function, providing PFC. Here 
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