If the wave equation of a particle is represented by, $y=0.8\sin \left(20\pi t-5\pi x+\frac{\pi }{4}\right)$, where $x$ and $y$ are measured in metre and $t$ is measured in seconds, then the wave equation represents a wave travelling in

The figure $\left(\mathrm{i}\right)$ shows the graphical representation of the air molecules in a tube of air ($\mathrm{length} = L$) at atmospheric pressure on the absolute pressure $P\left(x\right)$ graph. Which of following pictures corresponds to absolute pressure $P\left(x\right)$ of figure$\left(\mathrm{ii}\right)$?

Consider the following statements about sound passing through a gas.

$\left(\mathrm{A}\right)$ The pressure of the gas at a point oscillates in time.

$\left(\mathrm{B}\right)$ The position of a small layer of the gas oscillates in time.

Assertion: In sound waves variation of pressure and density of gas above and below average have a maximum value at a displacement node.

Reason: When particles on the opposite side of the displacement node approach each other gas between them is compressed and pressure rises so that at a displacement node gas undergoes the maximum amount of compression.