Question

For constructive interference the phase difference between two waves should be
$a) 0, \pi / 2, \pi.... \\ b) 0, 2 \pi, 4\pi.... \\ c) \pi, 3\pi, 5\pi... \\ d) \pi / 4, \pi/ 2, 3\pi/4...$
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Answer 1

0,2π,4π,6π,....

Constructive interference between two waves occurs when there path difference is equal to the integral multiple of λ.

For constructive interference, path difference Δx=nλ

Phase difference δ=

λ

2π

Δx

⟹ δ=

λ

2π

×nλ=2nπ

Hence for constructive interference, phase difference must be 0,2π,4π,6π,..

Answer 2

option c is the correct answer

hope it helps you