A passenger is sitting in a moving train whose engine is whistling. The frequency of the whistle heard by the passenger relative to the real frequency:

A wave equation is $y=0.1\sin \left(100\pi t-kx\right)$ and wave velocity is $100 \mathrm{m} {\mathrm{s}}^{-1}$, its wave number is equal to:

Two particles of a medium, disturbed by the wave propagation, are at $x_1=0 \mathrm{cm}$ and $x_2=1 \mathrm{cm}$. The respective displacements (in $\mathrm{cm}$) of the particles can be given by the equations:
$y_1=2\sin 3\mathrm{\pi }t$ and $y_2=2\sin (3\mathrm{\pi }t-\frac{\mathrm{\pi }}{8})$.
The wave velocity is

When we clap our hands, the sound produced is best described by (Here, $p$ denotes the change in pressure from the equilibrium value.)