If the seventh harmonic of a closed organ pipe is in unison with the fourth harmonic of an open organ pipe, then the ratio of the length of the closed pipe to that of the open pipe is:

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 $\,Hz$)

In a resonance tube,the first resonance is obtained when the level of water in the tube is at $16\,cm$ from the open end. Neglecting end correction,the next resonance will be obtained when the level of water from the open end is .... $cm$

An open organ pipe and a closed organ pipe of the same length $L$ produce $2$ beats per second when they are set into vibrations together in their fundamental modes. The length of the open pipe is made half and that of the closed pipe is doubled. The number of beats produced per second will be (neglect end correction).

$A$ cylindrical tube open at both ends has a fundamental frequency $f$ in air. When the tube is dipped vertically in water so that one-third part of the tube is in water,the fundamental frequency of the air column becomes (neglect end correction).

The pitch of an organ pipe is highest when the pipe is filled with