Please help with optics problem!!! I was wondering if anyone could help me out with the following optics problem: A prism, ABC, is configured such that angle BCA = 90 degrees and angle CBA = 45 degrees. What is the value of the index of refraction if, while immersed in the air, a beam incident on the face AC (at any angle) will be totally internally reflected from face BC. (In other words, what is the index of refraction for the prism so any incident angle on the face AC will give total internal reflection from face BC?) I am not sure how to approach this problem, and any help would be greatly appreciated. Thanks.