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MHT CET 2025 (23 Apr, Shift 1) · Prism, Dispersion & Scattering

Prism, Dispersion & Scattering question from MHT CET 2025 (23 Apr, Shift 1)

Q25MHT CET 2025 · 23 APR · SHIFT 1Medium

Prism, Dispersion & Scattering

A ray of light is incident on first face of an equilateral glass prism at an angle of incidence ' II '. The emergent ray just grazes along the adjacent face. The refractive index of the the prism is 2\sqrt{2}. The value of angle of incidence at first face is (sin⁡45∘=12,sin⁡90∘=1)\left(\sin 45^\circ = \frac{1}{\sqrt{2}}, \sin 90^\circ = 1\right)

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Answer: (a)

  1. Grazing emergence: r2=Cr_2 = C, sin⁡C=12⇒r2=45∘\sin C = \frac{1}{\sqrt{2}} \Rightarrow r_2 = 45^\circ.
  2. r1=60∘−45∘=15∘r_1 = 60^\circ - 45^\circ = 15^\circ
  3. sin⁡I=2sin⁡15∘⇒I=sin⁡−1(2sin⁡15∘)\sin I = \sqrt{2}\sin 15^\circ \Rightarrow I = \sin^{-1}(\sqrt{2}\sin 15^\circ)
  4. So the answer is (a).
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