In order for the refracted ray R to have the same direction in space as the incident ray I, shown above, which of the following conditions by itself would be sufficient? (A) n1=n2 (B) n1=n3 (C) n2=n3 (D) Plane surface P, is parallel to plane surface P2- (E) None of the conditions above would be sufficient by itself.
Index of refraction = speed of light / speed v
The Attempt at a Solution
I thought same direction means same angle from the normal line ,and for that to happen, their speeds must be equal. I am not sure if that’s correct ,but I answered it E, anyway. Am I right?