A point source emits sound equally in all directions in a non-absorbing medium. Two points $P$ and $Q$ are at a distance of $9\  meters$ and $25\  meters$ respectively from the source. The ratio of the amplitudes of the waves at $P$ and $Q$ is

The equation of a stationary wave is $Y = 10\,\sin \,\frac{{\pi x}}{4}\,\cos \,20\,\pi t$. The distance between two consecutive nodes in metres is

Two trains $A$ and $B$ initially $120\, km$ apart, start moving towards each other on the same track with a velocity of $60\, km/hr$ each. At the moment of start $A$ blows a whistle, which reflects on $B$ and subsequently reflects from $A$ and so on. Take the velocity of sound waves in air $1200\, km/hr$. The distance travelled by sound waves before the trains crash will be (in $km$)

In the standing wave shown, particles at the positions $A$ and $B$ have a phase difference of

The displacement $y$ of a wave travelling in the $x-$ direction is given by $y = {10^{ - 4}}\sin \left( {600t - 2x+\frac{\pi }{3}} \right)$ metre, where $x$ is expressed in metres and $t$ in seconds. The speed of the wave in $ms^{-1}$, is

A transverse harmonic wave on a string is described by $y = 3\sin \left( {36t + 0.018x + \frac{\pi }{4}} \right)$ where $x$ and $y$ are in $cm$ and $t$ in $s$. The least distance between two successive crests in the wave is .... $m$