CBSE Class 9 Answered

Dear Student

The girl sitting at the center of the park will hear two successive sounds: firstly, direct sound from the source & secondly the reflected sound from the wall.

If the time interval between these twe sounds that the girl hears is equal to or more than 1/10 second then an echo will be heard by the girl.

Dircet sound will reach the girl in : t1 = (6m)/(320m/s) = 0.01875 s

Reflected sound from the wall will reach after t2=(12m+6 m)/320m/s= 0.05625 s

Difference in the time interval = t2-t1= 0.0375s which is much less than persistance of hearing, 1/10=0.1 second.

Hence no echo will be heard.

Regards

Team

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