Question

In a resonance tube, the first resonance is obtained when the level of water in the tube is at $20cm$ from the open end. Neglecting end correction, the next resonance will be obtained when the level of water from the open end is

• A. $24cm$
• B. $32cm$
• C. $48cm$
• D. $60cm$

Answer 1

The correct option is C $48cm$

Initialy level of water at open end was

at $16cm$ depth

The first resonance will be when

wavelength ( $\lambda$ ) will be $\frac{\lambda }{4}$

Therefore $\frac{\lambda }{4}=16\Rightarrow \lambda =64$

Second resonance will be at $\frac{3\lambda }{4}$

let level of water is $lcm$ depth

$\frac{3\lambda }{4}=l$

$\frac{3\left(64\right)}{4}=l$

$l=48cm$