A magician during a show makes a glass lens with n = 1.47 disappear in a trough of liquid. What is the refractive index of the liquid ? Could the liquid be water ?

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.