In: Physics
The glass core of an optical fiber has an index of refraction 1.60. The index of refraction of the cladding is 1.49.
From Snell's Law we have n1 * sin(theta) = n2 * sin(90) =
n2
so theta = arcsin(n2/n1)
= arcsin(1.49 / 1.60) = 68.63 degree
But this angle is measured from the normal so from the wall the
angle
= 90 -68.63 = 21.37 degree