Question

A glass tube of 1.0 m length is filled with water. The water can be drained out slowly at the bottom of the tube. If a vibrating tuning fork of frequency 500 Hz is brought at the upper end of the tube and the velocity of sound is 330 m s–1, then the total number of resonances obtained will be

• A. 4
• B. 3
• C. 2
• D. 1

Answer 1

Answer: (B)

3

Answer 2

Wavelength,

$\lambda = \frac{Velocity}{Frequency} = \frac{330ms^{- 1}}{500s^{- 1}} = 0.66m$

The resonance occurs at

$\frac{\lambda}{4},\frac{3\lambda}{4},\frac{5\lambda}{4},\frac{7\lambda}{4},......$

i.e., at $0.165$m $0.495$m, $0.825$m, $1.155m$As the length of the tube is only $1.0m$, hence 3 resonances will be observed.