BITSAT 2018 Slot 2 Solved Paper

A planoconvex lens has thickness of 4cm. When placed on a horizontal table, with the curved surface in contact with it, the apparent depth of the bottom most point of the lens is found to be 3cm. If the lens is inverted such that the plane face is in contact with the table, the apparent depth of the centre of the plane face is found to be

25

8

cm. The focal length of the lens is (assume thickness of lens to be negligible)