Question

(n12) X (n21) refractive index in simplest form is

Answer 1

It is a problem of refractive index. n12 is the refractive index while the light travels from medium first to medium second. And similarly n21 is the refractive index when the light travels from the second medium to the first medium. By the principle of reversibility of the path of the light rays is reversible that means they travel in the same path in which it comes. Hence by this principle n12*n21 =1

Answer 2

It can be written as n12 ×n21=1. Refractive index is the proportion of the speed of radiation, (for example, light) in one medium, (for example, air, glass, or a vacuum) to that in another medium.

Refractive (Index of Refraction) is an esteem determined from the proportion of the speed of light in a vacuum to that in a second mechanism of more prominent thickness.