A light beam, passes from medium 1 to medium 2. Show that the emerging beam is parallel to the incident beam.

Answer

A, C

Explanation

Applying Snell's law at `A`,
`mu_1sini_1=mu_2sini_2`
or `mu_1/mu_2=sini_2/sini_1`……(i)
Similarly at `B, mu_2=sini_2=mu_1sini_3 `
`:. mu_1/mu_2=(sini_(2))/(sini_(3))`…….(ii)
From Eqs. (i) and (ii) ,we have , `i_3=i_1 `
i.e.the emergent ray is parallel to incident ray.