A railway engine whistling at a constant frequency moves with a constant speed. It goes past a stationary observer standing beside the  railway track. The frequency $(n)$ of the sound heard by the observer is plotted against time $(t).$ Which of the following best represents the resulting curve?

A transverse wave is described by the equation $y = {y_0}\,\sin \,2\pi \left( {ft - \frac{x}{\lambda }} \right)$ . The maximum particle velocity is equal to four times the wave velocity if

During propagation of a plane progressive mechanical wave incorrect statement is

Figure shows a sinusoidal wave at a given instant Which points are in same phase ?

A tuning of fork of frequency $392\, Hz$, resonates with $50\, cm$ length of a string under tension $(T)$. If length of the string is decreased by $2\%$, keeping the tension constant, the number of beats heard when the string and the tuning fork made to vibrate simultaneously is

A pulse shown here is reflected from the rigid wall $A$ and then from free end $B.$ The shape of the string after these $2$ reflection will be