Sir, Two plane mirrors M1 and M2 have a length of 2 meters each and are 10 cm apart. A ray of light is incident on one end of mirror M2 at an angle of 30 degrees. What is the number of reflections light undergoes before reaching the other end? I solved it in the following way: In each reflection the distance moved = 10 x tan(30) = 5.77 cm Therefore the number of reflections before it reaches the other end = 200/5.77 = 34 But the answer given in my book is 170. Please help.