A convergent beam of light passes through a diverging lens of focal length `0.2 m` and comes to focus at a distance of `0.3 m` behind the lens. Find the position of the point at which the beam would converge in the absence of the lens.

Explanation

Here, `f = -0.2m, v = + 0.3 m`
from lens equation
`(1)/(v)-(1)/(u)=(1)/(f)`
`(1)/(u)=(1)/(v)-(1)/(f)=(1)/(0.3)-(1)/(-0.2)=(25)/(3)`
`u = (3)/(25) = 0.12 m`
Therefore, in the absence of lens, the beam would coverge at a distance of `0.12 m` to the right of the concave lens.