Question

(i) What is an echo?
(ii) Define persistence of hearing.
(iii) Explain how the principle of echo is used by
the bat during its flight at night.​

Answer 1

Answer:

(i) The sound heard after reflection from a distant obstacle after the original sound has ceased, is called an echo.  

(ii) Two conditions for an echo to take place are:

(a) The minimum distance between the source of sound and the reflector must be 17m

(b) The minimum time taken by the reflected sound to reach the listener should be 0.1s

Explanation:

Answer 2

Answer:

(i)a sound or sounds caused by the reflection of sound waves from a surface back to the listener.

(ii)The sensation of hearing of any sound persists in our brain for 0.1s. This is called the persistence of hearing.

(iii)Bats use echolocation to navigate and find food in the dark. To echolocate, bats send out sound waves from the mouth or nose. When the sound waves hit an object they produce echoes. The echo bounces off the object and returns to the bats' ears.