Question

What is echo how is echo formed how thunder of clouds is formed?

Answer 1

The delay is proportional to the distance of the reflecting surface from the source and the listener. Typical examples are the echo produced by the bottom of a well, by a building, or by the walls of an enclosed room and an empty room. A true echo is a single reflection of the sound source.

Answer 2

ECHO=echo is the repetition of sound caused by the reflection of sound wave is called an echo
=an echo is simply a reflected sound