Question

what is echo? state two necessary conditions for echo to be heard. bats cannot see still they catch their prey? explain

Answer 1

Echo is a reflected sound heard after the original sound strikes a rigid obstacle...
The conditions are-
1- The reflecting surface should have a larger reflecting surface than the wavelength of the sound
2- The minimum distance to hear the echo should be 17m in air or as described by the formula Vt/2...
Bats cannot see but they use reflection of sound with an obstacle to find their prey...
hope it helps!!

Answer 2

An echo is a reflection of a sound which can be heard for a certain distance which between 100m and above conditions are the height of the wall must be greater than the wave length of the sound wave
the sound must me loud enough to hear an echo