Solving problems using Snell's Law

Question

A double pane surface consists of a layer of oil on top of a layer of water (index o1.333). A red laser beam (650nm) moves between the two surfaces, passing through the oil at a speed of 0.71c and into the water at a speed of 0.75c. The incident angle from the oil to the water boundary is 32 degrees. What is the index of refraction for the oil? What is the refracted angle, measured from the normal, for the red laser beam going into the water?

Answer 1

The index of refraction equals speed of light in vacuum divided by speed in the medium. For oil, n_o = c/v = c/0.71c = 1.408. Snell's law in this case: n_o sin 32° = n_w sin θ, sin θ = (1.408)(0.5299)/(1.333) = 0.5599, θ = 34.0° going from oil into water.