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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.
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Solution
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.
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