A thin plano- convex lens of focal length f is split into two halves one of halves is shifted along the optical axis. The separation b/w object and image plane is 1.8 m. The magnification of image formed by one of half lenses is 2. Find the focal length of lens and separation b/w the two halves.

Question

$(a)\;0.2\;m \\ (b)\;0.4\;m \\ (c)\;0.6\;m \\ (d)\;0.8 \;m$