An object is placed at 21 cm in front of a concave mirror of radius of a curvature 10 cm. A glass slab of thickness 3 cm and u 15 is then placed close to the mirror in the space between the object and the mirror. The position of final image formed is

Options

A. ``4.67cm
B. 6.67cm
C. 5.67cm
D. 7.67cm

Answer

d.

Explanation

`u=21cm, f=(R)/(2)=(10)/(2)=5cm`
On introducing the glass slab, the object as well as the image will be shifted from the mirror through a distance
`d=t(1-(1)/(mu))=3(1-(1)/(1.5))=1cm`, so that aparent distance of the object `=20cm ` i.e., `u=20cm`
By the mirror formula, `(1)/(v)+(1)/(u)=(1)/(f)`
`v=-(20)/(3)cm=-6.67cm`
Distance of the final image from the mirror `=6.67+1`
`=7.67cm`.