Question

The refractive index of glass is 1.5 and water is 1.33, what is the critical angle for glass water interface?
56°
62.5°
48°
54.6°

Answer 1

Answer:

by calculation its answer comes out to be 48

Answer 2

Answer:

The Correct Answer is 62.5°, i.e., for a glass-water interface, the critical angle is 62.5°.

Explanation:

Critical Angle is the incident angle to which the refracted angle in a rarer to denser medium is 90°. For an incident angle greater than the critical angle, the light rays starts showing Total Internal Reflection phenomena.

Let the Refractive Index of water w.r.t. glass be ¹n₂ and refractive index of glass w.r.t. be ²n₁.

Then according to formula, ¹n₂ = 1÷²n₁

By Snell's Law, sin b ÷ sin a = ᵇnₐ, where b is the angle of incident and a is the angle of refraction.

sin C ÷ sin 90° = 1 ÷ ²n₁

Sin C = 1 ÷ ²n₁

Sin C = n₂ ÷ n₁

Hence, putting n₂ = 1.33, n₁ = 1.5, we get :

Sin C = 1.33 ÷ 1.5

Sin C = 0.89

C = Sin⁻¹(0.89)

C = 62.5⁰