$\frac{\lambda}{2}=\mathrm{L} ; \mathrm{v}=\mathrm{f}_0 \lambda$
$\frac{\mathrm{v}}{2 \mathrm{f}_0}=\mathrm{L} \Rightarrow \mathrm{v}=2 \mathrm{Lf}_0$
$\mathrm{~L}^{\prime}=\frac{\mathrm{v}}{2 \mathrm{f}^{\prime}}=\frac{2 \mathrm{Lf}_0}{2 \mathrm{f}^{\prime}}$
$=\frac{L f_0}{\mathrm{f}^{\prime}}=\frac{90 \times 400}{600}=60$

Statement $1:$ In the resonance tube experiment, if the tuning fork is replaced by another identical turning fork but with its arm having been filled, the length of the air column should be increased to obtain resonance again.
Statement $2:$ On filling the arms, the frequency of a tuning fork increases.
$I.$ Waves created on the surfaces of a water pond by a vibrating sources.
$II.$ Wave created by an oscillating electric field in air.
$III.$ Sound waves travelling under water.
Which of these can be polarized