Question

An object is placed in front of a mirror at a distance of `60cm`. If its two times diminished image is formed on the screen, the focal length of the mirror is
A. `20cm`
B. `45cm`
C. `15cm`
D. `90cm`

Answer 1

Correct Answer - A
`M=(-v)/(u)=(-1)/(2)impliesv=(u)/(2)=-30cm`
`(1)/(f)=(1)/(v)+(1)/(u)impliesf=-20cm`