Light is confined and conducted down a long string of glass called an optical fiber. The figure below shows the end of an optical fiber where the light enters. A ray of light enters at an angle, a. What must be the index of refraction of the fiber, nf, in order for all the light that enters the fiber to be totally internally reflected? Hint: this means that when a-90, then 8-90. nair nair a nf 8