Question

A 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 also 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 metre per second, then n is-

Answer 1

The frequency of the vibration of tuning fork is 1000 Hz

Explanation :

When the piston is moved to 8.75 cm, the path difference produced

= 2 x 8.75

= 17.5 cm

we know that for intensity to become minimum from maximum, the wavelength difference is equal to λ/2, hence

λ/2 = 17.5

=> λ = 35 cm = 0.35 m

Given speed of sound = v = 350 m/s

we know that frequency = speed/wavelength

=> n = 350/0.35

=> n = 1000 Hz

Hence the frequency of the vibration of tuning fork is 1000 Hz