The intensity of sound increases at night due to

The enclosed air inside a closed box of rigid walls has pressure $P_1$. The density of air inside this box is constant. On heating the gas, the pressure of the enclosed air is increased from $P_1$ to $P_2$. Now it is observed that the sound travels $1.4$ times faster than at pressure $P_1$. The ratio $P_2/P_1$ is:

What is the distance between consecutive condensation and rarefaction in longitudinal waves?

Derive the expression for the speed of a sound wave and obtain the equations for the speed of sound in different media.

At what temperature (in $^\circ C$) will the speed of sound in air be $3$ times its value at $0^\circ C$ (in $^\circ C$)?

Match the following:

Column-$I$	Column-$II$
$(a)$ Transverse wave through a steel rod	$(i)$ $\sqrt{B + \frac{4}{3} \frac{\eta}{\rho}}$
$(b)$ Longitudinal waves in earth's crust	$(ii)$ $\sqrt{\frac{\eta}{\rho}}$
$(c)$ Longitudinal waves through a steel rod	$(iii)$ $\sqrt{\frac{2 \pi T}{g \lambda}}$
$(d)$ Ripples	$(iv)$ $\sqrt{\frac{Y}{\rho}}$