When a glass lens with `mu` = 1.47 is immersed in a trough of liquid, it looks to be disappeared. The liquid in the trough could be

Explanation

The refractive index of the liquid must be equal to 1.47 in order to make the lens disappear. This means` n_(1) = n_(2)` . This gives `1//f =0 or f rarr oo`. The lens in the liquid will act like a plane sheet of glass. No, the liquid is not water. It could be glycerine.