A whistle ' $S$ ' of frequency $f$ revolves in a circle of radius $R$ at a constant speed $v$. What is the ratio of maximum and minimum frequency detected by a detector $D$ at rest at a distance $2 R$ from the center of circle as shown in figure? (take ' $c$ ' as speed of sound)

An organ pipe $P_1$ closed at one end vibrating in its first overtone. Another pipe $P_2$  open at both ends is vibrating in its third overtone. They are in a resonance with a  given tuning fork. The ratio of the length of $P_1$ to that of $P_2$ is

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 ..... $m$

Four tuning forks of frequencies $200,201, 204$ and $206\, Hz$ are sounded together.  The beat frequency will be

The phase difference corresponding to path difference of $x$ is

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