Question

A girl is sitting in the middle of a park of dimension 12 m × 12 m. On the left side of it, there is a building adjoining the park and on the right side of the park, there is a road adjoining the park. A sound is produced on the road by a cracker. Is it possible for the girl to hear the echo of this sound? Explain your answer.

Answer 1

If the time gap between the original sound and reflected sound received by the listener is around 0.1 s, only then the echo can be heard.
Speed of sound in air, v=344 ms⁻¹ 

The time gap between the original sound and the reflected sound received by the girl

= `18/344"S" - 6/344 "S"`

= 0.035s

As 0.035 s < 0.1 s, therefore no echo will be heard by the girl.