1. The problem statement, all variables and given/known data 2. Relevant equations 3. The attempt at a solution I have solved this problem . For that I had to use refraction at the first surface , then reflection from the back side and then again refraction from the first surface . This gives me the correct answer . But when I saw the solution given I was quite surprised by the method employed . Please see the solution . In this they consider the apparent position of the mirror (as if the mirror has shifted towards the object) .This is something similar when we look at the bottom surface of the pool and it appears nearer . Even though this method gives the correct answer and is shorter, I wonder whether it is correct to employ this approach . My objection is that the light rays have to actually travel all the way to the mirror so as to undergo reflection . In the pool case , it is the apparent shift which the observer standing from outside sees . I would appreciate if someone could help me understand the validity of the above given solution .