For a particular resonance tube,following are four of the six harmonics below $1000 \,Hz$: $300, 600, 750$ and $900 \,Hz$. The two missing harmonics are:

An open organ pipe having fundamental frequency $(n)$ is in unison with a vibrating string. If the tube is dipped in water so that $75 \%$ of the length of the tube is inside the water,then the ratio of the fundamental frequency of the air column of the dipped tube to that of the string will be (Neglect end corrections).

An air column in a closed organ pipe vibrating in unison with a tuning fork produces the second overtone. The vibrating air column has:

The fundamental frequency of a closed pipe is $400 \,Hz$. If $1/3$ of the pipe is filled with water,the frequency of the $2^{\text{nd}}$ harmonic of the pipe will be (Neglect end correction). (in $\,Hz$)

$A$ 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

$A$ pipe $30 \, cm$ long is open at both ends. Which harmonic mode of the pipe resonates with a $1.1 \, kHz$ source? (Speed of sound in air $= 330 \, m/s$)