Question

To hear the echo of a sound distinctly, the reflecting surface in air should be at a minimum distance of $$p$$ from the listener. Then $$p$$ should be ______.

Options

• 7 m

• 10 m

• 15 m

• 17 m

Answer 1

To hear the echo of a sound distinctly, the reflecting surface in air should be at a minimum distance of $$p$$ from the listener. Then $$p$$ should be 17 m.

Explanation:

For a distinct echo, the reflected sound should reach the listener after at least \(0.1\,\text{s}\).

\[ 2p = vt \]

Taking the speed of sound in air as \(340\,\text{m s}^{-1}\),

\[ p=\frac{340\times0.1}{2}\]

\[ =\frac{34}{2}\]

= 17 m