OPTICAL PATH LENGTH

1. In a medium of constant refractive index , n , the product of the geometric distance and the refractive index. 2. In a medium of varying refractive index, the integral of n s , where s is an element of length along the path , and n is the local refractive index. ( 188 ) Note: Optical path length is proportional to the phase shift that a lightwave undergoes along a path.