We know that, v=λf, then, λ=fv=340Hz340ms−1=340s−1340ms−1=1m
First resonating length, l1=4λ=4100=25cm
Second resonating length, l2=43λ=43×100=75cm
Third resonating length, l3=45λ=45×100=125cm
So third resonance is not possible since the length of the tube is 125cm
Thus, minimum height of water necessary for resonance =125−75=50cm
