A point object at 15 cm from a concave mirror of radius of curvature 20 cm is made to oscillate along the principal axis with amplitude 2 mm. The amplitude of its image will be

Options

A. `2 mm`
B. `4 mm`
C. `8 mm`
D. None of these

Answer

C

Explanation

`1/v+1/(-15)=(1)/(-10) implies v= -30cm`
`m=-(v/u)=-(-30)/(-15)=-2`
`|(Delta v)|=m^(2) | (Deltau)|=(-2)^(2) (2 mm)`
`=8 mm`.