Explain total internal reflection?

When a ray of light moves a denser to a rarer medium it bends away from the normal at the point of incidence. That means the angle of refraction > angle of incidence. Now if we go on increasing the angle of incidence, at a particular value of the incidence angle, the corresponding angle of refraction becomes equal to 90 degrees and the refracted ray of light grazes the surface of separation. This value of the angle of incidence is known as the critical angle. If we continue to increase the angle of incidence beyond the critical angle, the ray of light do not enter the rarer medium but is totally reflected internally in the denser medium. This is known as the phenomenon of total internal reflection.For a total internal reflection to take place, (i) the light ray should pass from a denser to a rarer medium and (ii) the angle of incidence should be greater than the critical angle for the two given media. Two examples of total internal reflection are (a) mirage and (b) sparkling of diamonds. read less

Total internal reflection is an interesting phenomenon that occurs when a travelling wave strikes the boundary between two mediums, at a greater angler than the critical angle wrt the normal to the surface. If the RI of the 2nd medium is lower and the incident angle is greater than the critical angle, the wave cannot pass through and is entirely reflected. read less