ECE532 Biomedical Optics ©1998 Steven L. Jacques, Scott A. Prahl Oregon Graduate Institute | |

Chapter 4 Course Home | ## Time-resolved Monte Carlo:## Introduction |

We are already familiar with the simple Beer's Law description of photon survival in an absorbing medium:

## survival = exp(-µ
| where µ _{a} = absorption coefficient [cm^{-1}]L = pathlength of photon travel [cm] |

In a scattering medium, the photon's path is not a straight line, but Beer's law still holds. Regardless of how tortuous the path, the pathlength is given by:

## L = ct | where c = the speed of light in the medium (c = c _{o}/n)t = time [s] |

At any point in time, one can calculate the probability of photon survival by exp(-µ_{a}L) = exp(-µ_{a}ct).