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Wave Optics question

2024 · 31 Jan · Shift 2 · Q74
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Wave Optics question

2024 · 31 Jan · Shift 2 · Q74

JEE MainPhysicsWave OpticsMCQ+4 / −1
When unpolarized light is incident at an angle of 60∘60^{\circ}60∘ on a transparent medium from air, the reflected ray is completely polarized. The angle of refraction in the medium is:
  1. A
    60∘60^{\circ}60∘
  2. B
    90∘90^{\circ}90∘
  3. C
    30∘30^{\circ}30∘
  4. D
    45∘45^{\circ}45∘
View written solutionFree

Correct answer: C

  1. Identify the condition for complete polarization

When the reflected ray is completely polarized, the angle of incidence is the Brewster angle iBi_BiB​.

So here, iB=60∘i_B = 60^\circiB​=60∘

  1. Use Brewster's law

At Brewster's angle, μ=tan⁡iB\mu = \tan i_Bμ=taniB​

Also, an important relation at Brewster's angle is: iB+r=90∘i_B + r = 90^\circiB​+r=90∘ where rrr is the angle of refraction.

  1. Calculate the angle of refraction

Given, iB=60∘i_B = 60^\circiB​=60∘

Therefore, r=90∘−60∘=30∘r = 90^\circ - 60^\circ = 30^\circr=90∘−60∘=30∘

  1. Check options
  • A: 60∘60^\circ60∘ ❌
  • B: 90∘90^\circ90∘ ❌
  • C: 30∘30^\circ30∘ ✅
  • D: 45∘45^\circ45∘ ❌

Hence, the correct answer is: 30∘\boxed{30^\circ}30∘​

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