Question

Two stationary sources of sound, $S_{1}$ and $S_{2}$ having an equal frequency are fixed some distance apart. The position $A$ is left of $S_{1}$ , position $B$ in the middle of the two sources and position $C$ is to the right of $S_{2}$ . An observer starts moving with velocity $V_{0} \, $ from position $A$ towards $S_{1}$ , then

• A. beats for three position $A,B$ and $C$ will be heard
• B. beats will be heard from $A$ and $C$ but not in case of $B$
• C. beats will be not heard for $A$ and $C$ but will be heard for $B$
• D. beats will be not heard for three position of $A,B$ and $C$

Answer 1

Answer: (C)

At point, $A$ and $C$ two sounds are approaching from both the two sources and the listener is either moving towards sources or going away from sources.
But at point $B$ cases are not same as mentioned in the previous condition at point $A$ or $C$ , hence beat is produced as the listener is moving away from $S_{1}$ and approaching towards $S_{2}$