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

A point source emits sound equally in all directions in a non-absorbing medium. Two points $P$ and $Q$are at distances of $2m$ and $3m$ respectively from the source. The ratio of the intensities of the waves at $P$ and $Q$ is

A man is watching two trains, one leaving and the other coming with equal speed of $4\,m/s$ . If they sound their whistles each of frequency $240\, Hz$ , the number of beats per sec heard by man will be equal to: (velocity of sound in air $= 320\, m/s$ )

A wave travelling in the $-ve\,\,z-$ direction having displacement along $x-$ direction as $1\,m,$ wavelength $\pi\, m$ and frequency at $\frac {1}{\pi }\,H_Z$ is represented by

The length of an open organ pipe is $0.5\, m$. Calculate the fundamental frequency of the pipe, if the velocity of sound in air be $350\, m/sec$   .... $Hz$

For a certain organ pipe three successive resonance frequencies are observed at $425\, Hz,595 \,Hz$ and $765 \,Hz$ respectively. If the speed of sound in air is $340 \,m/s$,  then the length of the pipe is ..... $m$