A light ray entering an optical fiber (made from crown glass) surrounded by air is first refracted and then reflected as shown below. 7 7 a. What is the minimum angle 0 (greater than or equal to 0) at which an incident ray will still be totally internally reflected? Minimum angle 0 = deg. (Only enter values 0 or greater.) b. What is the maximum angle 0 (smaller than 90 deg) at which an incident ray will still be totally internally reflected? Maximum angle 0 = 20 deg. c. If the optical fiber is made with material other than crown glass, what minimum value 12 is needed for refractive index of the material to ensure that all incident rays are totally internally reflected? Minimum n needed - = 3.