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

Explanation

The lens ofrefractive index same as of liquid will be invisible in that liquid As `n_1 = 1.47` , then refractive index of lens `n_2 = 1.47`
From lens maker.s formula
`1/f = ((n_1 - n_2)/(n_2))[1/R_1 - 1/R_2]`
`1/f = ((n_2-n_2)/(n_2))[1/R_1 - 1/R_2]`
`= (0) [ 1/R_1 - 1/R_2]`
`therefore f = 1/0 = " infinity " (oo)`
Hence, lens will behave as plane surface in liquid.
`rArr` No, this liquid can.t be water because its refractive index is `(4)/(3)`, This liquid can be glycerine.