Infrasound can be heard by

Give two applications of ultrasound.

$(i)$ What does the acronym $SONAR$ stand for?
$(ii)$ What is the audible range of sound for human beings?
$(iii)$ How do the bats search and catch their prey in dark night?

Flash of lightning reaches earlier than the sound of thunder. Why?

What is echo ranging? State any one application of this technique.

State whether the following statement is true or false:
The wavelength of $5\, MHz$ ultrasound in a medium where the velocity is $1540\, m s^{-1}$ is $0.3\, mm$.