A-LevelPhysicsSuperposition9702/12 · Feb/Mar 2025 · Q271 Mark

Light waves are emitted from two sources. What is a necessary condition for observable interference fringes to be produced?

AThe waves must be polarised.

BThe waves must not be polarised.

CThe waves must be coherent.

DThe waves must have equal amplitudes.

✓ Correct answer

C: The waves must be coherent.

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Topic: Superposition, A-Level Physics (syllabus 9702). Multiple choice, 1 mark.
Source: A-Level Physics, Feb/Mar 2025 Paper 1 Variant 2, question 27.

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