Refraction problems due Midnight!! Problem 13. A ray of light traveling in air strikes the midpoint of one face of an equiangular glass prism (n=1.65) at angle of exactly 30.0 degrees. Trace the path of the light ray through the glass and find the angle of incidence of the ray at the bottom of the prism. Answer in degrees. Note: The triangle is 60-60-60 degrees. I don't know where to start. Problem 15. Light strikes the surface of a prism, n=1.78. If the prism is surrounded by a fluid, what is the maximum index of refraction of the fluid that will still cause total internal reflection within the prism? Note: The triangle is 90-45-45 triangle. I don't no where to start.