In a resonace tube experiment, the first resonance is obtained when the level of the water in the tube is at 20 cm from the open end. Resonace will also be obtained when the distance of the water level from the open end is

Options

A. 40 cm from the open end
B. 60 cm from the open end
C. 80 cm from the open end
D. 100 cm from the open end

Explanation

For 1st resonance (1/4) `lambda=L`
`rArr lambda=4L` …(i)
For 2nd resonance
`3(lambda/4)=L_2 rArr lambda=(4L_2)/3` ….(ii)
By using (i) and (ii)
`(4L_2)/3=4L`
`rArr L_2=3L=3 (20)=60` cm
Similarly, `L_3` = 5L = 100 cm