When an object is at a distance 3 meters and 1meters from the optical centre of a convex lens, a real and virtual image are formed respectively, with the same magnification. Find the focal length of the lens (in meters)

Answer

2

Explanation

`[2]`
`f/(-u_(1)+f)=-f/((-u_(2)+f))implies-u_(2)+f=u_(1)-fimpliesf=(u_(1)+u_(2))/2=2`