Example $33\mathrm{.}1$ Material a is water and material b is glass with index of refraction $1\mathrm{.}52.$ The incident ray makes an angle of $60$ degrees with the normal. a$)$ nd the directions of the re ected and refracted rays. b$)$ Find the speed of light in water and the one in glass. c$)$ Find the critical angle for water and the one for glass