  Light propagation in an infinite uniform turbid medium is treated as a Markov
stochastic process of photons to provide an intuitive framework for photon
migration. The macroscopic physical quantities of photon migration are shown to
be completely determined by the microscopic statistics of the photon
propagation direction in direction space and a generalized Poisson distribution
of the number of scattering events that includes an exponential decay
absorption factor. A proper diffusion solution is derived with an exact
time-dependent central position and half width of photon migration in this
framework. The diffusion coefficient is found to be absorption-independent.
