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

A. 500 Hz
B. 1000 Hz
C. 2000 Hz
D. 4000 Hz

Answer 1

Correct Answer - B
Additional path difference introduced when the piston is moved through 8.75 cm = `2xx8.75`= 17.50 cm
Since, the intensity changes from a maximum to a minimum additional path = `lamda//2`
`therefore" "(lamda//2)=17.50 or lamda=35.0` cm
Velocity, `v=350" m "s^(-1) = 35000" cm "s^(-1)`
`therefore "Frequency",upsilon=(v)/(lamda)=(35000)/(35)=1000" Hz"`