Vibrating tuning fork of frequency $n$ is placed near the open end of a long cylindrical tube. The tube has a side opening and is fitted with a movable reflecting piston. As the piston is moved through $8.75\ cm,$ the intensity of sound changes from a maximum to minimum. If the speed of sound is $350\ m/s.$ then $n$ is [image:15_image38.png]

Question

Dr. Abubacker · Accepted Answer

(b) When the piston is moved through a distance of $8.75cm,$ the path difference produced is $2 	imes 8.75cm = 17.5cm.$
This must be equal to $\frac{\lambda}{2}$ for maximum to change to minimum.
$	herefore\frac{\lambda}{2} = 17.5\ cm \Rightarrow \lambda = 35cm = 0.35m$
So, $v = n\lambda \Rightarrow n = \frac{v}{\lambda} = \frac{350}{0.35} = 1000Hz$

Explanation

Reviewed by Dr. Abubacker

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