The diagram shows the propagation of a progressive wave. $A$,$B$,$C$,$D$,$E$,and $F$ are points on this wave. Which of the following points are in the same state of vibration (i.e.,in the same phase)?

$A$ plane progressive wave propagating along the positive $x$-axis is represented by:

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

The equation of a progressive wave is $Y = a \sin 2 \pi (n t - \frac{x}{5})$. The ratio of maximum particle velocity to wave velocity is

$A$ transverse harmonic wave on a string is described by $y(x, t) = 3.0 \sin (36t + 0.018x + \pi/4)$,where $x$ and $y$ are in $cm$ and $t$ is in $s$. The positive direction of $x$ is from left to right.
$(a)$ Is this a travelling wave or a stationary wave? If it is travelling,what are the speed and direction of its propagation?
$(b)$ What are its amplitude and frequency?
$(c)$ What is the initial phase at the origin?
$(d)$ What is the least distance between two successive crests in the wave?

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