4. In the figure below, an empty chamber (top half) is placed on top of a slab of green glass (bottom half). Multiple laser rays are incident at a single spot at the bottom of the green glass. The laser rays are either reflected or refracted at the glass-air interface. a) Pick one light ray, take necessary measurements directly on the figure. Use trigonometry to calculate the angle of incidence and the angle of refraction. b) Determine the refractive index of the green glass. c) Calculate the critical angle for total internal reflection at the glass-air interface