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A 20cm thick glass slab of refractive in...

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.

Text Solution

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Shifting in object due to glass slab x =`d(1-(1)/(mu)) = 20[1-(1)/(1.5)] = (20)/(3) "cm"`
Distance of object from mirror (as seen by mirror) =`40 - (20)/(3) = (100)/(3) "cm"`
Image will be formed at a distance `(100)/(3)` cm from mirror `M`.
Shifting in image due to glass slab = `(20)/(3)` cm
So distance of image from mirror = `(100)/(3) - (20)/(3) = (80)/(3) "cm"`

Distance of image from the actual plane mirror is independent of separation b between glass slab and mirror. If the distance is more than brightness of image will be less.
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