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JEE Main 2022 (25 Jun, Shift 1) · Total Internal Reflection

Total Internal Reflection question from JEE Main 2022 (25 Jun, Shift 1)

Q27JEE Main 2022 · 25 JUN · SHIFT 1Medium

Total Internal Reflection

A light wave travelling linearly in a medium of dielectric constant 4, is incident on the horizontal interface separating medium with air. The angle of incidence for which the total intensity of incident wave will be reflected back into the same medium will be:

(Given: relative permeability of medium μ\mur = 1)

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Answer: (d)

  1. n=εrμr=4×1=2n = \sqrt{\varepsilon_r \mu_r} = \sqrt{4\times1} = 2.
  2. sin⁡C=1n=12⇒C=30∘\sin C = \frac{1}{n} = \frac{1}{2} \Rightarrow C = 30^\circ.
  3. All the light is reflected only when i>30∘i > 30^\circ; of the options only 60∘60^\circ qualifies.
  4. So the answer is (d) 60∘60^\circ.
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