Question

An object O is kept infront of a converging lens of focal length `30` cm behind which there is a plane mirror at 15 cm from the lens.

A. the final image is formed at `60 cm` from the lens towards right of it
B. the final image is at `60 cm` from lens towards left of it
C. the final image is real
D. the final image is virtual.

Answer 1

Correct Answer - b,c
`(1)/(f)=(1)/(v)-(1)/(u) (1)/(+30)=(1)/(v)-(1)/(-15)`
`(1)/(v)=(1)/(30)-(1)/(15)=-(1)/(30) v=-30`
For plane mirror
`u=-30-15=-45 cm rArr v=+45 cm`
For second refraction
`u=-60, f=30 cm`
`(1)/(30)=(1)/(v)-(1)/(-60) (1)/(v)=(1)/(30)-(1)/(60)=-(1)/(60) v=+60 cm`
final image is real and `60 cm` left from lens.