Question

(2 points) Optical fibers are made of glass, where light is trapped inside the fiber by total internal reflection. This example is not a fiber geometry and doesn't include the gradations in refractive index that are used, but still illustrates the point of total internal reflection. Suppose you have a piece of glass, with light incident from the glass side toward an air interface. The refractive index of the glass is 1.45. What is the critical angle where all light will be reflected back into the glass? Are angles greater or less than this critical angle fully reflected back into the glass? Note that the angles are defined as the angle away from normal incidence, using the reference system where normal incidence is 0°, as shown in the figure below

Answer 1

If angle is greater than the critical angle, all the light is reflected back into the glass.

If angle is lesser than the critical angle, some light will be reflected back while some will get refracted.