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Question 20253
JEE Physics · Medium

Electromagnetic Waves and Wave Optics: YDSE — Monochromatic vs White Light MCQ

Solve this quality-checked JEE multiple-choice question, then review the correct answer and explanation.

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YDSE — Monochromatic vs White LightMediumQuestion 20253

Question

In YDSE with white light, a bright fringe of wavelength λ₁ at order n₁ coincides with a bright fringe of λ₂ at order n₂ when:
  1. A
    λ₁/λ₂ = n₂/n₁
  2. B
    λ₁n₁ = λ₂n₂
    Correct
  3. C
    n₁/n₂ = λ₁/λ₂
  4. D
    Both n₁ = n₂ and λ₁ = λ₂

Correct answer

λ₁n₁ = λ₂n₂

Explanation

Position of bright fringe: y = nλD/d. For two wavelengths to coincide: n₁λ₁D/d = n₂λ₂D/d → n₁λ₁ = n₂λ₂. This gives missing orders and spectral overlaps in gratings.

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