In a thick glass slab of thicknes l, and refractive index `n_(1)`, a cuboidal cavity of thickness 'm' is carved as shown in figure, and is filled with a liquid of `R.I. n_(2)(n_(1)gtn_(2)).` The ratio `l//m`, so that shift produced by this slab is zero when an observer A observes an object B with paraxial rays is

Options

A. `(n_(1)-n_(2))/(n_(2)-n_(1))`
B. `(n_(1)-n_(2))/(n_(2)(n_(1)-1))`
C. `(n_(1)-n_(2))/(n_(1)-1)`
D. `(n_(1)-n_(2))/(n_(1)(n_(2-1))`

Answer

b.

Explanation

Shift `=(l-m)(1-(1)/(n_(1)))+m(1-(1)/(n_(2)))=0`