Question

Mcsuperbx1
18:43
a plano-convex lens has a thickness of 4 cm. When placed on a horizontal table with curved surface in contact with it, the apparent depth of the bottom-most point of the lens is found to be 3 cm. If the lens is inverted such that the plane face is contact with the table, the apparent depth of the centre of plane face is found to be 25/8 cm. The focal length of the lens is?

Answer 1

Answer:

sorry I can't understand