Question

An object is placed at a distance of `20cm` from a equi-concave lens of focal length `30cm`, whose one surface is silvered. If the radius of curvature of the silvered surface is `60cm`, find the position and nature of the image.

Answer 1

`(-1)/(F)=(2)/(f)-(1)/(f_(m))=(2)/(-30)-(1)/(+30)=-(3)/(30)`
`rArrF=+10cm`
`:. (1)/(F)=(1)/(v)+(1)/(u)`
`rArr (1)/(10)=(1)/(v)+(1)/(-20)`
`rArrv=+20//3cm`
as `m=-(v)/(u)=-(-20//3)/(-20)=(1)/(3)`
`:.` Image will be virtual, errect and diminished.