Question

To demonstrate the phenomenon of interference of sound, we need:

• A. two sources, which emit sound of exactly the same frequency
• B. two sources, which emit sound of exactly the same frequency and have a definite phase relationship
• C. two sources, which emit sound of exactly the same frequency and have a varying phase relationship
• D. two sources, which emit sound of exactly the same wavelength

Answer 1

Answer: (B)

two sources, which emit sound of exactly the same frequency and have a definite phase relationship

For demonstration of interference of sound we need two coherent source, of same frequency with constant phase difference

$P_1=P_{01}sin(Kx-\omega t)$

$P_2=P_{02}sin\left(k\right(x+\Delta x)-\omega t)$

$=P_{02}sin(Kx-\omega t+\delta )$

$\delta =K\Delta x=\frac{2\pi \Delta x}{\lambda }$