Transport length


The transport length in a strongly diffusing medium is the length over which the direction of propagation of the photon is randomized. It is related to the mean free path l by the relation:
with:
g: the asymmetry coefficient. or averaging of the scattering angle θ over a high number of scattering events.
g can be evaluated with the Mie theory.

If g=0, l=l*. A single scattering is already isotropic.

If g→1, l*→infinite. A single scattering doesn't deviate the photons. Then the scattering never gets isotropic.
This length is useful for renormalizing a non-isotropic scattering problem into an isotropic one in order to use classical diffusion laws. The transport length might be measured by transmission experiments and backscattering experiments.