Question

what is total internal reflection?

Answer 1

total internal reflection means the complete reflection of a light ray reaching an interface with a less dense medium when the angle of incidence exceeds the critical angle.

eg: reflection in diamond

Answer 2

When a ray of light passes from a denser medium to a rare medium. If the angle of incidence is greater than the Critical angle then the ray is reflected back in the denser medium. This type of reflection of light is called total internal reflection.