Question

A turning fork vibrating with frequency of $500Hz$ is kept close to the open end of tube filled with water, as shown in figure. The water level in the tube is gradually lowered. When the water level is $17cm$ below the open end, maximum intensity of sound is heard. If the room temperature is ${20}^{o}C$, the speed of sound in air at this temperature is then

• A. $330m{s}^{-1}$
• B. $340m{s}^{-1}$
• C. $350m{s}^{-1}$
• D. $360m{s}^{-1}$

Answer 1

Answer: (B)

$340m{s}^{-1}$

Here, $\nu =500Hz,L=17cm=17\times {10}^{-2}m$
For open organ pipe, the fundamental frequency in terms of the velocity is given by:

$\nu =\frac{v}{4L}$

$\therefore v=\nu \left(4L\right)$

$v=\left(500s^{-1}\right)(4\times 17\times {10}^{-2}m)$

$\Rightarrow 340m{s}^{-1}$