Recall that traveling waves have a wave speed that can be calculated by v = f . Recall also that the index of refraction also relates v (light's effective travel speed through a medium) to c (its speed in a vacuum): n = c/v. Now note that the frequency of a wave's periodic disturbances does not change when that wave crosses a boundarye.g., from medium #1 into medium #2. So, which of the following equations must be true? Group of answer choices n1/ 1 = n2/2 n1 1 = n2 2 c1/(n1 1 )= c2/(n2 2) f1 = f2