What is the index of refraction for this block of quartz?

In order to answer this problem, you need to know Snell's Law which is sin(theta)1 x n1= sin(theta)2 x n2. In this problem treat 30.4 degrees as theta1 and 20.1 degrees as theta2. the index of refraction of air is n=1. So you do sin(30.4)/sin(20.1) which should equal 1.47...which should be the answer.