A beam of light is travelling from region II to region III (see the figure). The refractive index in the region I, II and III are n 0 , n 0 2 , and n 0 2 respectively. The angle of incidence θ for which the beam just misses entering region III is

Question

A beam of light is travelling from region II to region III (see the figure). The refractive index in the region I, II and III are n 0 , n 0 2 , and n 0 2 respectively. The angle of incidence θ for which the beam just misses entering region III is, 30 °, 45 °, 60 °, sin - 1 ⁡ 2

MARKS App · Accepted Answer

The critical angle for region II and III sin ⁡ C = μ I I I μ I I = n 0 2 n 0 2 = 1 2 i e . ∠ C = 45 ° The ray, if incident at 45 ° at the interface of II and III it will be totally internally reflected. Now, from Snell's lay in region I and II. n 0 sin ⁡ θ = n 0 2 sin ⁡ C O r sin ⁡ θ = 1 2 × sin ⁡ 45 ° O r sin ⁡ θ = 1 2 × 1 2 O r sin ⁡ θ = 1 2 O r θ = 30 °

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