Question

A closed organ pipe, of length 1.2 m and filled with a gas, is resonated in its fundamental mode with the some fork. Another open pipe of same length but filled with air resonates with the same fork. The room temperature is 40${}^o$C. If the speed of sound in air at 40${}^o$ C is 360 m/s, then the speed of sound in gas at 40${}^o$C will be:

• A. 637 m/s
• B. 683 m/s
• C. 341.5 m/s
• D. 720 m/s

Answer 1

The correct option is D 720 m/s

Frequency at closed end is, $f=\frac{\lambda }{4l}$

Frequency at open end is, $f=\frac{{\lambda }_2}{2l}$

$\therefore {\lambda }_2=2\lambda$

$V_2=f{\lambda }_2\Rightarrow V_2=720m{s}^{-1}$