I'm confused on this question. I would show my work, but I'm not sure on how to even approach the question. The book labels this problem as straight forward, but I still don't see it and I'm confused on which formula(s) to use.. A narrow white light beam is incident on a block of fused quartz at an angle of 30.0 deg. Find the angular width of the light beam inside the quartz. I tried to use Snell's law, but don't see how. My book shows no specific formulas under the dispersion and prisms section. Any help is greatly appreciated. Thanks.