Question

The velocity of sound in air is 330 m/s. Calculate the minimum distance between a source of sound and a reflecting wall, so that a clear echo may be heard. Take the time of persistence of the sound to be 0.1 s.

Answer 1

Step 1- Given Data

velocity of sound in air is$330m/s$.

Time taken by the sound to be heard $t=0.1s$

Step 2- To find out the distance between the source and the wall.

Let the distance between the wall and source is $d$.

The echo is heard by the observer after it travels a distance $2d$.

Formula for distance -

$Dis\tan ce\left(2d\right)=Speed\left(v\right)\times time\left(t\right)$

$$\begin{gathered} \Rightarrow 2d=v\times t \\ \Rightarrow d=\frac{v\times t}{2} \\ \Rightarrow d=\frac{330\times 0.1}{2}=16.5m. \end{gathered}$$

Thus, the minimum distance between a source of sound and a reflecting wall is $16.5m.$