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

Given,

Speed of sound (v) = 342 ms^-1

Time taken for hearing the echo (t) = 3 s

Distance travelled by sound = v × t = 342 × 3 = 1026 m

In 3 s, sound has to travel twice the distance between the reflecting surface and the source.

Hence, the distance between reflecting surface from the source

= $\dfrac{1026}{2}$ = 513 m