As we know, frequency
$f \propto \sqrt{m g}$ or $f \propto \sqrt{g}$
In water, $f _{ w }=0.8 f _{ air }$
$\frac{ g ^{\prime}}{ g }(0.8)^2=0.64$
$\Rightarrow 1-\frac{\rho_{ w }}{\rho_{ m }}=0.64$
$\Rightarrow \frac{\rho_{ W }}{\rho_{ m }}=0.36$
In liquid, $\frac{ g ^{\prime}}{ g }=(0.6)^2=0.36$
$1-\frac{\rho_1}{\rho_{ m }}=0.36 \frac{\rho_1}{\rho_{ m }}=0.64$
From eq. $(1)$ and $(2)$
$\frac{\rho_l}{\rho_n}=\frac{0.64}{0.36} \quad \therefore \quad \rho_l=1.77$
${y}=1.0\, {mm} \cos \left(1.57 \,{cm}^{-1}\right) {x} \sin \left(78.5\, {s}^{-1}\right) {t}$
The node closest to the origin in the region ${x}>0$ will be at ${x}=\ldots \ldots \ldots\, {cm}$
