BITSAT 2022 Paper

Given, first resonance column at deoth, l1=24cm
Second resonance column at depth, l2=78cm
Third resonance column at depth, l3=?
Asl1+x=

λ

4

=24...............(i)
l2+x=

3λ

4

=78................(ii)
l3+x=

5λ

4

................(iii)
From Eqs. (i) and (ii),
x=

l2−3l1

2

=

78−3(24)

2

=3..................(iv)
substituting l1 and x value, we get
l3=5(24)+4(3)
⇒l3=132cm.