The figure shows some light rays reflected from a small defect in the glass toward the surface of the glass. (a) If c = 40.00,

The figure shows some light rays reflected from a small defect in the glass toward the surface of the glass.
(a) If θc = 40.00°, what is the index of refraction of the glass?
(b) Is there any point above the glass at which a viewer would not be able to see the defect? Explain.