Question

The pitch of an open organ pipe at constant temperature corresponding to fundamental frequency is highest when the pipe is filled with

• A. nitrogen
• B. hydrogen
• C. oxygen
• D. chlorine

Answer 1

The correct option is B hydrogen

We know that pitch depend on the frequency of sound.
For open organ pipe, fundamental frequency,
$f=\frac{v}{2l}$, ...........(1)
where $l$ is the length of an organ pipe.
Also, speed of sound in gaseous medium,
$v=\sqrt{\frac{\gamma RT}{M}}$ ...........(2)
At constant temperature and for diatomic gases,
$f\propto \frac{1}{\sqrt{M}}$
[from (1) and (2)]
So, lighter gas will have higher frequency thus higher pitch.