This is the question: The optical path length of a light beam is nd where n is the refractive index and d is the physical distance. A light beam passes through 2.0 in thick glass (n=1.525) and then through 12 in. of water (n=1.33) and finally though 0.6 in of polystyrene (n=1.590). What is the optical path length? Is this too easy to just multiply the refractive index by the length and then add all of those numbers? When I did that I got about 20 inches. I was also wondering if I missed a trick or anything in this problem. The length could be different (instead of using the values of 2 in, 12 in, and 0.6 in) because the light becomes bent (with the refractive index). Does this set up a triangle in the glass, water, and polystrene? Is only the one side of the triangle 2 in and i am looking for the hypotenuse as a length value? If so how would i calculate that with no angles (or only a 90 degree one)? Thanks for reading.