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Question 20201
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Electromagnetic Waves and Wave Optics: Coherence Condition MCQ

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Coherence ConditionEasyQuestion 20201

Question

For a stable and observable interference pattern, the two sources must be:
  1. A
    Very bright
  2. B
    Coherent — same frequency and constant phase difference
    Correct
  3. C
    Moving rapidly
  4. D
    Widely separated

Correct answer

Coherent — same frequency and constant phase difference

Explanation

Incoherent sources (like two independent lamps) have rapidly varying phase differences, so the interference pattern averages out to uniform illumination. Coherent sources (derived from the same source) maintain a fixed phase relationship.

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