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What is meant by an echo? Explain.

Answer» <html><body><p></p>Solution :An echo is a repetition of sound produced by the reflection of sound waves from a wall, <a href="https://interviewquestions.tuteehub.com/tag/mountain-565001" style="font-weight:bold;" target="_blank" title="Click to know more about MOUNTAIN">MOUNTAIN</a> or other obstructing surfaces. The speed of sound in air at `20^(@)`C is 344 `m s^(-1)`. If we <a href="https://interviewquestions.tuteehub.com/tag/shout-1206524" style="font-weight:bold;" target="_blank" title="Click to know more about SHOUT">SHOUT</a> at a wall which is at 344 m away, then the sound will take 1 second will take one more second to reach us. <a href="https://interviewquestions.tuteehub.com/tag/therefore-706901" style="font-weight:bold;" target="_blank" title="Click to know more about THEREFORE">THEREFORE</a>, we hear the echo after two seconds. <br/> Scientists have estimated that we can hear two <a href="https://interviewquestions.tuteehub.com/tag/sounds-1219274" style="font-weight:bold;" target="_blank" title="Click to know more about SOUNDS">SOUNDS</a> properly if the time gap or time interval between eachsound is `(1/10)^(th)` of a second (persistence of hearing) i.e., 0.1 s. Then, <br/> Velocity `=("Distance travelled")/("time taken") =(<a href="https://interviewquestions.tuteehub.com/tag/2d-300662" style="font-weight:bold;" target="_blank" title="Click to know more about 2D">2D</a>)/t` <br/> 2d= `344 xx 0.1 = 34.4` m<br/> d= 17.2 m<br/> The minimum distance from a sound reflecting wall to hear an echo at `20^(@)` C is 17.2 meter.</body></html>


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