A point object is placed at distance of 20 cm from a thin plane - convex lens of focal length 15 cm . The plane surface of the lens is now silvered . The image created by the system is :-

Options

A. 60 cm to the left of the system
B. 60 cm to the right of the system
C. 12 cm to the left of the system
D. 12 cm to the right of the system

Answer

C

Explanation

Refraction from lens is : `(1)/(v_(1)) - (1)/(-20) = (1)/(15)`
`therefore v = 60 cm + "ve direction "`
i.e., first image is formed at 60 cm to the right of lens system.
Reflection from mirror : After reflection from the mirror , the second the image will be formed at a distance of 60 cm to the left of lens system
Refraction from lens : `(1)/(v_(3)) - (1)/(60) = (1)/(15) leftarrow +ve`
direction or `v_(3) = 12 cm`
Therefore , the final image is formed at 12 cm to the left of the lens system .