A person wants a real image of his own, 3 times enlarged. Where should he stand in front of a concave mirror of radius of curvature of 30cm.

Options

A. 90cm
B. 10cm
C. 20cm
D. 30cm

Answer

C

Explanation

Given, ,=-3, and R=30cm
`f=(R )/(2)=-15cm`
We know that `m=-(v)/(u) Rightarrow -3=(-v)/(u)`
v=3u
`"Also" (1)/(f)=(1)/(v)+(1)/(u) `
`(1)/(-15)=(1)/(3u)+(1)/(u)Rightarrow (-1)/(15)=(1+3)/(3u)`
`-3u=4xx15`
`Rightarrow u=(-4xx15)/(3)`
Initial position of a person, u=-20cm