Question

When two waves with same frequency and constant phase difference interfere,

• A. there is a gain of energy
• B. there is a loss of energy
• C. the energy is redistributed and the distribution changes with time
• D. the energy is redistributed and the distribution remains constant in time

Answer 1

The correct option is D the energy is redistributed and the distribution remains constant in time

The energy at a point due to wave is proportional to the square of the amplitude.
When two waves with the same frequency and constant phase difference interfere, the energy is redistributed because the resultant amplitude$\left(A_0\right)$ is given by,

$A_0^2=A_1^2+A_2^2+2A_1{A}_2\cos \varphi$

Where, $A_1$ and $A_2$ are the amplitudes of the two waves and $\varphi$ is the phase difference. Since, $\varphi$ is constant here, so $A_0$ remains constant in time. Thus, the energy is redistributed and remains constant in time.

Hence, $\left(D\right)$ is the correct answer.