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CBSE Class 9 Answered

short note on ECHO
Asked by santhamma658 | 06 Jan, 2016, 04:35: PM
answered-by-expert Expert Answer

Hi John,

The repetition of sound caused by reflection of sound waves from an obstacle is known as 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 and reflected sound must be at least 0.1 s. If we take the speed of sound to be 344 m/s at a given temperature, say at 22°C in air, then the total distance covered by the sound from the point of generation to the reflecting surface and back should be at least (344 m/s) × 0.1 s = 34.4 m. Thus, for hearing distinct echoes, the minimum distance of the obstacle from the source of sound must be 17.2 m.

Answered by | 06 Jan, 2016, 06:16: PM

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