Question

An echo returned in $3s$. What is the distance of the reflecting surface from the source, given that the speed of sound is ${342ms}^{-1}$?

• A. $520m$
• B. $515m$
• C. $530m$
• D. $513m$

Answer 1

The correct option is D $513m$

If $d$ be the distance between reflecting surface and the source.

For the echo, the sound travels distance $2d$ in $3s$.

Thus, $2d=vt$ or $d=vt/2=\frac{342\times 3}{2}=513m$