Question

In a long cylindrical tube, the water level is adjusted and the air column above it is made to vibrate in unison with a vibrating tuning fork kept at the open end. Maximum sound is heard when the air column lengths are equal to :

• A. $\frac{\lambda }{4},\frac{\lambda }{2},\frac{3\lambda }{4}$
• B. $\frac{\lambda }{4},\lambda ,\frac{3\lambda }{2}$
• C. $\frac{\lambda }{2},\frac{3\lambda }{2},\frac{5\lambda }{2}$
• D. $\frac{\lambda }{4},\frac{3\lambda }{4},\frac{5\lambda }{4}$

Answer 1

Answer: (D)

Resonance takes place when
$\ell =\frac{\lambda }{4}$
$\ell =\frac{3\lambda }{4}$
$\ell =\frac{5\lambda }{4}$