A wide slab consisting of two media of refractive indices n 1 and n 2 is placed in air as shown in the figure. A ray of light is incident from medium n 1 to n 2 at an angle θ , where sin θ is slightly

Question

A wide slab consisting of two media of refractive indices $n_{1}$ and $n_{2}$ is placed in air as shown in the figure. A ray of light is incident from medium $n_{1}$ to $n_{2}$ at an angle $θ$ , where $\sin θ$ is slightly larger than $\frac{1}{n_{1}}$ . Take refractive index of air as $1$ . Which of the following statement(s) is (are) correct?

TestHub · Accepted Answer

Option A: If n 1 = n 2 , n 1 sin θ = n 2 sin θ 1 . . . 1 and n 2 sin θ 1 = 1 × sin r . . . 2 From (1) and (2), sin r = n 1 sin θ Now, sin θ > 1 n 1 , (given) ∴ sin r > 1 (which is not possible) and hence light will reflect back from air , n 2 interface Option B: If n 2 < n 1 , Snell's law at A , n 1 sin θ = n 2 sin θ 1 . . . 3 Snell's law at B n 2 sin θ 1 = sin r . . . ( 4 ) From 3 and ( 4 ) , n 1 sin θ = sin r ∴ sin r > 1 (not possible) Hence, light might reflect from A or B . Option C: If n 2 > n 1 , n 1 sin θ = n 2 sin θ 1 . . . 5 at A n 2 sin θ = 1 × sin r . . . 6 at B ∴ n 1 sin θ = 1 × sin r ∴ sin r > 1 (not possible) ∴ Light will reflect back into medium n 1 . Option D: If n 2 = 1 , n 1 sin θ = n 2 sin θ 1 ⇒ sin θ 1 = n 1 sin θ or sin θ 1 > 1 not possible Hence, light will reflect back into the medium.

Physics - Geometrical Optics Question with Solution | TestHub

Options:(select one or more)

Doubts & Discussion