Among the following,the equation representing a progressive wave is
$(A)$ $y=2 \cos 3x \sin 10t$
$(B)$ $y=2 \sqrt{x-vt}$
$(C)$ $y=3 \sin (5x-0.5t)+4 \cos (5x-0.5t)$
$(D)$ $y=\cos x \sin t+\cos 2x \sin 2t$

Which of the following statements is incorrect during the propagation of a plane progressive mechanical wave?

Distance travelled by a progressive wave having wavelength $\lambda$ and frequency $\nu$ in time $t$ is ......

The figure given below shows four progressive waves $A, B, C$ and $D$ with their phases expressed with respect to the wave $A$. It can be calculated from the figure that

$A$ progressive wave is represented by $y=12 \sin (5 t-4 x) \ cm$. On this wave,how far away are the two points having a phase difference of $90^{\circ}$?

The diagram below shows an instantaneous position of a string as a transverse progressive wave travels along it from left to right. Which one of the following correctly shows the direction of the velocity of the points $1, 2$ and $3$ on the string?