A-LevelPhysicsSuperposition9702/12 · Feb/Mar 2021 · Q281 Mark

Two sources of microwaves P and Q produce coherent waves with a phase difference of 180°. The waves have the same wavelength λ. [Figure 28.1] At the point S there is a minimum in the interference pattern produced by waves from the two sources. The distance (QS – PS) is called the path difference. Which expression could represent the path difference?

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Aλ / 4

Bλ / 2

Cλ

D3λ / 2

✓ Correct answer

C: λ

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Topic: Superposition, A-Level Physics (syllabus 9702). Multiple choice, 1 mark.
Source: A-Level Physics, Feb/Mar 2021 Paper 1 Variant 2, question 28.

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