Question

Derive the expression Sinc =n2/n1​

Answer 1

the easiest way is to start with n_1\sin \theta _i = n_2\sin \theta _r . Note that at a critical angle of incidence, the angle of refraction is 90 degrees and you know that the sine of 90 degrees is 1.

\implies n_1 \sin \theta _c = n_2  

\implies \sin \theta _c = \frac{n_2}{n_1} , where n_1 is the optically denser medium

Answer 2

Answer:

this is my explanation in own words