An Optical Fiber Having Index of Refraction 1 $^{\circ}$ B) 268 $^{\circ}$

Multiple Choice

An optical fiber having index of refraction 1.40 is clad with a material of index of refraction 1.25.What is the critical angle for this fiber?

A) 63.2 $^{\circ}$
B) 26.8 $^{\circ}$
C) 41.8 $^{\circ}$
D) 73.0 $^{\circ}$
E) 16.5 $^{\circ}$