Question

The echo will be heard if the original sound reflected by an obstacle reaches our ears after

• A. 10 s
• B. 5 s
• C. 1 s
• D. 0.1 s

Answer 1

The correct option is D 0.1 s

The sensation of any sound persists in our ear for about 0.1 seconds. This is known as the persistence of hearing. If the echo is heard within this time interval, the original sound and its echo cannot be distinguished. So the most important condition for hearing an echo is that the reflected sound should reach the ear only after a lapse of at least 0.1 second after the original sound dies off.