Question

A tuning fork of frequency 340 Hz resonates in the fundamental mode with an air column of length 125 cm in a cylindrical tube closed at one end. When water is slowly poured in it, the minimum height of water required for observing resonance once again is ____ cm.
(Velocity of sound in air is 340 ms–1)

Answer 1

The correct answer is 50
Given :
$340=\frac{n}{4×125}v$
⇒ n = 5
So λ = 100 cm
So minimum height is
$\frac{λ}{2}=50$ cm