Light enters a solid pipe made of plastic having an index of refraction of 1.60. The light travels parallel to the upper part of the pipe (Fig. E33.17). You want to cut the face AB so that all the light will reflect back into the pipe after it first strikes that face.

(a) What is the largest that θ can be if the pipe is in air?

(b) If the pipe is immersed in water of refractive index 1.33, what is the largest that θ can be?

Figure E33.17