Combination of Lenses question from NEET 2003 (AIPMT)

Answer: (a)

1. Cut along XOX' (the principal axis): each half keeps both curved surfaces, so $f' = f$.
2. Cut along YOY' (the plane of the lens): each half is plano-convex, $\frac{1}{f''} = \frac{\mu-1}{R} = \frac{1}{2f}$, so $f'' = 2f$.
3. So the answer is (a) $f' = f$, $f'' = 2f$.