An echo is returned in 3 s. What is the distance of the reflecting surface from the source, considering the speed of sound as 342 ms-1?

An echo is returned in 3 s. What is the distance of the reflecting surface from the source, considering the speed of sound as 342 ms-1? Correct Answer 513 m

CONCEPT:

• Echo: If we shout or clap near a suitable reflecting object such as a tall building or a mountain, we will hear the same sound again a little later. This sound which we hear is called an echo.
  • Echoes are heard due to the phenomenon of Reflection of sound waves.
  • To hear the echo clearly, the reflecting object must be more than 17.2 m from the sound source for the echo to be heard by a person standing at the source.

Calculation:

Given that,

 An echo is returned after time (t) = 3s

Speed of the sound (v) = 342 m/s

Now according to the law's of motion distance traveled by sound waves can be given as 

Distance travelled (d) = v x t

          = 342 × 3

          = 1026m

Distance covered by the sound will double, as the sound will have to travel and source to reflecting surface and back from it hence distance will be ‘d’ is ‘2d.

• Now replacing ‘d’ with ‘2d’ we get

          2d = 1026

          d = 513 m

• The distance from the reflecting surface to the source is 513 m.