Question

define echo. expain the conditions for hearing an echo

Answer 1

An echo is a reflection of sound, arriving at the listener some time after the direct or original sound. The main conditions for hearing an echo are:-
1) There should be minimum distance of 17 m between the source of sound and the reflector.
2) There should be a time gap of 0.1 sec between the original sound and the sound received after reflection.

Answer 2

Echo :

The reflection of sound from a distant obstacle ( hill , any hard obstacle , polished substance ) 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 .

(iv) The time to reach the echo should be minimum 0.1 s .