Draw a ray diagram. represent the light beam with one ray. draw a line normal to the boundary. do this at each point where the ray intersects a boundary. show the ray bending in the correct direction. the angle is larger on the side with the smaller index of refraction. this is the qualitative application of snell’s law. label angles of incidence and refraction. measure all angles from the normal. use snell's law. calculate the unknown angle or unknown index of refraction. follow the steps above to solve the problem: a diamond is underwater; a light ray enters one face of the diamond, then travels at an angle of 30 degrees with respect to the normal. what was the ray's angle of incidence on the diamond? the index of refraction of water is nwater=1.33, and the index of refraction of diamond is ndiamond=2.42.