"Where should a second hole be placed in order for the light [...]?" 1. The problem statement, all variables and given/known data The problem and the solution are attached as jpg files. (Given that the problem depends on the drawing, I think it's more convenient for the reader to view the text in the image as well.) 2. Relevant equations Snell's Law: ##n_1 sin θ_1 = n_2 sin θ_2## 3. The attempt at a solution In the TheSolution.jpg, I don't, mathematically, get how it can it say ##2.54 sin 48.6° = 1.0 sin θ_2## since that would mean that ##asin(2.54 sin(48.6°))## would not exist (but, I do get total internal reflection when thinking about it theoretically rather than mathematically). Also, how is the leftmost 11.4° angle (from the normal) found to be 11.4°? Any input would be greatly appreciated!