Question

Question #08234

Answer 1

We know the mirror formula as below

`color(blue)(1/v+1/u=2/r)`

where

`u->"object distance"=-20cm`

`v->"image distance"`

`r->"radius of curvature"`

Here it is also given that size of the virtual image seen behind the mirror is twice that of object.This means the magnification `m=-2`

Again `m=v/u=>-2=v/u`

So `v=-2u=-2xx(-20)cm=40cm`

Inserting these values in mirror equation we get

`color(green)(1/v+1/u=2/r)`

`=>1/40+1/-20=2/r`

`=>(1-2)/40=2/r`

`=>r=-80cm`