Question

The echo of a sound is heard after 5 seconds. If the speed of sound in air be 342 m/s, calculate the distance of the reflecting surface.

Answer 1

An echo is heard when a sound hits any hard surface and the reflected sound reaches back to our ears.

Let the distance of the reflecting surface = d

Speed of the sound in air = 342 m/s

Time taken by an echo to be heard = 5 seconds

Total distance travelled by the sound waves = 2d

$$\begin{gathered} \therefore 2d=342\mathrm{m}/\mathrm{s}\times 5\mathrm{s} \\ \Rightarrow d\mathit{}=\frac{342\mathrm{m}/\mathrm{s}\times 5\mathrm{s}}{2}=855\mathrm{m} \end{gathered}$$