Question

What is an echo ?
What are the minimum conditions for an echo to be heard ?

Answer 1

It is the sound formed up by the reflection of sound waves.

Conditions necessary for echo are:-

1) The distance between the source and reflecting surface must be more than 17 meters.

2) The time period of hearing the echo must be more than 0.1 seconds.


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Answer 2

Echo :

The reflection of sound from a distant obstacle after the original sound has ceased is called an echo .

The conditions are as follows :

(i) The minimum distance should be 17 m between the reflecting surface and source.

(ii) The intensity of sound should be large enough .

(iii) The size of reflector should be large enough .