An object is placed at a distance of `40 cm` from a concave mirrorr of focal length `15 cm`. If the object is displaced through a distance of `20 cm` towards the mirrorr, the displacement of the image will be

Options

A. 30 cm towards the mirror
B. 36 cm away from the mirror
C. 30 cm away the mirror
D. 36 cm towards the mirror

Answer

B

Explanation

Applying `1/v + 1/u = 1/f`
`u = -40 implies 1/v - 1/40 = 1/(-15)`
`implies v = 24 cm " " ....(i)`
Now `u = -20`
`implies 1/v - 1/20 = 1/15 implies v = -60 " "....(ii)`
From eq (1) and (2)
Image moves 36 cm away mirror