A `20cm` thick glass slab of refractive index `1.5` is kept in front of a plane mirror. Find the position of the image (relative to mirror) as seen by an observer through the glass slab when a point object is kept in air at a distance of `40 cm` from the mirror.

Explanation

O will act as a object for glass slab form image I at a distance
`x = d [ 1- (1)/( mu)] = 20 [1- (1)/(1.5)] = (20)/(3 ) cm`

So the glass slab will shift the mirror from MM to mm Distance of ojbect from this virtual plane mirro
`= 40 - x = 40 - (20)/( 3) = (100)/(3) cm`
virtual mirror mm will form the image of object O at a distance `(100)/(c )` cm behind the actual mirror Mm
`:. ,` mm is `(20)/( 3 )` cm in front of MM
`:. ,` distance of image from the actual plane
distance of image from the actual plane mirror is independent of separation b between glass slab and the mirror . If the distance is more than brightness of image will be less