The drawing shows a ray of light traveling through three materials whose surfaces are parallel to each other. The refracted rays (but not the reflected rays) are shown as the light passes through each material. A ray of light strikes the a?b interface at a 50.0Â° angle of incidence. The index of refraction of material a is na = 1.20. The angles of refraction in materials b and c are, respectively, 47.3Â° and 57.0Â°. Find the indices of refraction in these two media. I found nb but i cant find what nc is. Solution using snell\'s law n b sin(theta) b = n a sin(theta) a n b = n a sin(theta) a / sin(theta) b n b =1.2508 Similarly, n c = n b sin(theta) b / sin(theta) c n c = 1.09605 .