$A$ glass tube of $1 \,m$ length is filled with water. The water can be drained out slowly from the bottom of the tube. If a vibrating tuning fork of frequency $500 \,Hz$ is brought at the upper end of the tube, then the total number of resonances obtained are [Velocity of sound in air is $320 \,m/s$].

An open pipe of length $l$ vibrates in its fundamental mode. The pressure variation is maximum at

The fifth harmonic of a closed organ pipe is found to be in unison with the first harmonic of an open pipe. The ratio of lengths of closed pipe to that of the open pipe is $5 / x$. The value of $x$ is . . . . . . .

An aluminium rod having a length $100 \,cm$ is clamped at its middle point and set into longitudinal vibrations. Let the rod vibrate in its fundamental mode. The density of aluminium is $2600 \,kg/m^3$ and its Young's modulus is $7.8 \times 10^{10} \,N/m^2$. The frequency of the sound produced is .............. $Hz$.

$A$ closed organ pipe of length $L_1$ and an open organ pipe contain diatomic gases of densities $\rho_1$ and $\rho_2$ respectively. The compressibilities of the gases are same in both pipes,which are vibrating in their first overtone with the same frequency. The length of the open organ pipe is (Neglect end correction).

$A$ wire of length $L$ and linear density $m$ is stretched between two rigid supports with tension $T$. It is observed that the wire resonates in the $P^{th}$ harmonic at a frequency of $320 \text{ Hz}$ and resonates again at the next higher frequency of $400 \text{ Hz}$ in two successive modes. The value of $P$ is