[SOLVED] Internal Reflection Problem 1. The problem statement, all variables and given/known data (please check attachment for figure) ni = 1 nr = 1.48 theta_I = 50 degrees l = 3.1 mm w = 42 cm Find N (Number of reflections before laser beam finally emerges). 2. Relevant equations Snell's Law: ni sin theta_I = nr sin theta_r 3. The attempt at a solution My attempt at the solution was to first find angle of refraction, and I found it using Snell's Law. Theta_r = 30 degrees Then, if you check the figure I attached, I formed an extension and completed the triangle. Using this, I found angle of incidence. Theta_I = 90-30 = 60 degrees Afterwards, I got a triangle of the complete ray. I drew the triangle in the figure I attached. I had Y, which is (l = 3.1 mm). I need to find x, so I used the tangent ratio . x = (3.1 x 10^-3) tan(60) = 5.4 x 10^-3 m Then, I used the following ratio: N= w/x = (42 x 10^-2) / (5.4 x 10^-3) = 77.8 I rounded the value up to get 78. I don't know, but I'm afraid that I might have done a mistake. Can someone please go over my solution and check if I'm correct? Thanks, Jin EDIT: Whilst someone approves my attachment, here's the problem text: A laser beam traveling in air strikes the midpoint of one end of a slab of material as shown in Figure 15-24. The index of refraction of the slab is 1.48. Determine the number of internal reflections of the laser beam before it finally emerges from the opposite end of the slab.