If $v_{\mathrm{rms}}=$ root mean square speed of molecules,

$v_{\text{av }}=$ average speed of molecules

$v_{\mathrm{mp}}=$ most probable speed of molecules;

$v_s=$ speed of sound in a gas

Then, identify the correct relation between these speeds.

The production of echo is due to

As a wave propagates, which of the following is a wrong option?

The amplitude of the sound is doubled and the frequency is reduced to one fourth. The intensity of sound at the same point will be