Question

Explain "reversibility of light".

Answer 1

The principle of reversibility states that light will follow exactly the same path if its direction of travel is reversed. When light is incident on the surface of separation of two media, it gets deviated from its original path. Let us take an example to understand this better. If a ray of light travels from medium 1 to medium 2, it has a certain angle of incidence and angle of refraction, say 60 and 45 degrees. Now if you reverse the direction of the ray of light, such that it now travels from medium 2 to medium 1, then the ray of light will get refracted in move in the same path, such that its angle of refraction and angle of incidence gets reversed. Thus in the above example, if we reverse the direction of the ray of light, the angle of incidence becomes 45 and the angle of refraction becomes 60. This is the principle of reversibility of light.