# Optical fiber cable

Glass-fiber-guided light beams are continuously reflected at the interface between glass and air. How large is the maximum angle $$\gamma$$ (half opening angle) of the exiting light at the end of the glass fiber, in degrees, to the nearest integer?

The glass has a refractive index of $$n = 1.38,$$ while the air has an index of $$n = 1.$$

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