Question

For constructive interference, the phase difference between two waves reaching at a point is 

(A) Zero

(B) \(\pi\) 

(C) \(\frac{\pi}{2}\) 

(D) \(\frac{3\pi}{2}\)

Answer 1

Correct option is (A) Zero

Constructive interference between two waves occurs when there path difference is equal to the integral multiple of \(\lambda\).

For constructive interference, path difference \(\Delta = n\lambda\)

Phase difference, \(\delta = \frac {2\pi}{\lambda} \Delta x\)

\(\Rightarrow \lambda = \frac {2 \pi}\lambda \times n \lambda = 2 n\pi\)

Hence for constructive interference, phase difference must be \(0, 2 \pi, 4\pi, 6\pi,....\).

Answer 2

Correct option is: (A) Zero