Let \(n_g=\) ref. index of glass, \(n_l=\) ref. index of liquid, \(f_l=\) focal length of liquid
\(\frac 1{f_l}=\left(n_g-1\right)\left[\left(\frac 1{R_1}\right)-\left(\frac 1{R_2}\right)\right]\)
For \(f_l={\infty}\) (to make glass disappear), \(n_g=n_l\) ,
\(n_l=1{\cdot}47\) , thus it will behave as a plane glass.
No, the liquid can not be water because it’s ref. index is not \(1.33.\)