The wavelength of one wave is $99 \ cm$ and that of another is $100 \ cm$. If the speed of sound is $396 \ m/s$,the number of beats heard per second is:

$A$ tuning fork vibrates with $2$ beats in $0.04$ seconds. The frequency of the fork is .... $Hz$.

Two tuning forks have frequencies $380 \, Hz$ and $384 \, Hz$ respectively. When they are sounded together,they produce $4 \, beats$ per second. After hearing the maximum sound,how long will it take to hear the minimum sound?

$56$ tuning forks are arranged in increasing order of frequencies in a series such that each fork gives $4 \text{ beats per second}$ with the previous one. The frequency of the last fork is the octave of the first. The frequency of the first fork is ..... $Hz$.

$A$ set of $20$ tuning forks is arranged in a series of increasing frequencies. If each fork gives $4 \; Hz$ beats with respect to the preceding fork and the frequency of the last fork is twice the frequency of the first,then the frequency of the last fork is $\dots \; Hz$.

$A$ wave has simple harmonic motion whose period is $4\; s$,while another wave which also possesses simple harmonic motion has its period $3\; s$. If both are combined,then the resultant wave will have the period equal to ....... $s$.