An Unclad Optical Fiber Has Index of Refraction 1

Multiple Choice

An unclad optical fiber has index of refraction 1.40. What is the acceptance angle for this fiber if it is submerged in a fluid with index of refraction 1.30? The acceptance angle is the greatest angle at which the light enters the end of the fiber and still causes total internal reflection.

A) 69.0°
B) 23.6°
C) 45.8°
D) Any angle will be accepted.