Verified Solution • 2025–26 Session moderate

QJEEM22Ph8159: JEE Main 2022 Physics - Class 12 JEEM22Ph8159 Solution: A light wave travelling linearly in a medium of dielectric…

A light wave travelling linearly in a medium of dielectric constant 4, incidents 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\mu r = 1)

Multiple Choice Options

  • A 10 ∘^\circ
  • B 20 ∘^\circ
  • C 30 ∘^\circ
  • D 60 ∘^\circ

Step-by-Step Verified Solution

n=Kμ=2n = \sqrt {K\mu } = 2 (n ⇒\Rightarrow refractive index)

So for TIR

\theta > {\sin ^{ - 1}}\left( {{1 \over n}} \right)

\theta > 30

Only option is 60 ∘^\circ

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