The correct figure that shows,schematically,the wave pattern produced by the superposition of two waves of frequencies $9\,Hz$ and $11\,Hz$ is:

Three sound waves of equal amplitudes have frequencies $(f-1)$,$f$,and $(f+1)$. They superpose to produce beats. The number of beats produced per second will be:

Two tuning forks with frequencies $380 \,Hz$ and $384 \,Hz$ are sounded together. They produce $4$ beats per second. What is the time interval between the maximum sound and the next minimum sound?

Two strings $X$ and $Y$ of a sitar produce a beat frequency of $4 \ Hz$. When the tension of the string $Y$ is slightly increased,the beat frequency is found to be $2 \ Hz$. If the frequency of $X$ is $300 \ Hz$,then the original frequency of $Y$ was .... $Hz$.

$A$ tuning fork $A$ of unknown frequency produces $5 \, beats/s$ with a fork of known frequency $340 \, Hz$. When fork $A$ is filed,the beat frequency decreases to $2 \, beats/s$. What is the frequency of fork $A$ in $Hz$?

$50$ tuning forks are arranged in increasing order of their frequencies such that each gives $4 \, \text{beats/sec}$ with its previous tuning fork. If the frequency of the last fork is the octave of the first, then the frequency of the first tuning fork is ... $Hz$.