wave_mechanics critical_thinking Question 42
Question: 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
Options:
A) 500 Hz
B) 1000 Hz
C) 2000 Hz
D) 4000 Hz
Show Answer
Answer:
Correct Answer: B
Solution:
When the piston is moved through a distance of 8.75cm, the path difference produced is $ 2\times 8.75cm=17.5cm $ .
This must be equal to$ \frac{\lambda }{2} $ for maximum to change to minimum.
\ $ \frac{\lambda }{2}=17.5 $ cm
Therefore $ \lambda =35cm=0.35m $ So, $ v=n\lambda $
Therefore $ n=\frac{v}{\lambda }=\frac{350}{0.35}=1000Hz $
BETA
