Question

what is an echo for class 9​

Answer 1

Answer:

The sound returning back towards the source after reflection from a distant obstacle(a wall, a hill,etc.) is called echo.

Answer 2

Explanation:

Phenomneon of hearing back our own sound is called echo. It is used to succesive reflection of sound waves from the surface orobstacles of large size. To hear an echo , there must be atime gap of 0 .1 second in original sound and the reflected sound.