Question

A plano-convex lens has a thickness of 4 cm. 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 3 cm. 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 of the lens is found to be 25/8 cm.
1: Find focal length of lens assuming a thin lens
a) 75 cm b) 72 cm
c) 70 cm d) 68 cm
2: Find focal length of lens assuming a thick lens
a) 75 cm b) 72 cm
c) 70 cm d) 68 cm​

Answer 1

Answer:

answer is c

answer of 2 nd Question is a