Echo
Echo
Echo: When a person shouts in a big empty hall, we first hear his original sound, after that we hear the reflected sound of that shout. This reflected sound is an echo. An echo is nothing but just the reflected sound. So, the repetition of sound caused by reflection of sound waves is called an echo. The sensation of sound persists in our brain for about 0.1 s. To hear a distinct echo, the time interval between the original sound and the reflected one must be atleast 0.1 s. The speed of sound in air is 344 m/sec. The distance travelled by the sound in 0.1 s = speed x time = 344 x 0.1 = 34.4 m
So, echo will be heard, if the minimum distance between the source of sound and the obstacle is = .
Conditions for the formation of Echoes
Q. A man stands in between two cliffs x and y, such that he is at a distance of 66 m from x. When he blows a whistle he hears first echo after 0.4 s and second echo after 1.2 s. Calculate: (i) speed of sound (ii) distance of the cliff y from man.
Solution: (i) Speed of sound
(ii) Distance of man from cliff
The time interval between a lightning flash and the sound of thunder was found to be 5sec. If the speed of sound in air is 330m/sec . Find the distance of the flash from the observer. | |||
| Right Option : B | |||
| View Explanation | |||
An echo returned in 0.3 s. What is the distance of the reflecting surface from the source of sound ? (Speed of sound is | |||
| Right Option : D | |||
| View Explanation | |||
An echo retured in 3 s. What is the distance of the reflecting surface from the source, given that the speed of sound is 342 m/sec ? | |||
| Right Option : D | |||
| View Explanation | |||
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