Combination of Lenses question from NEET 2023

Answer: (b)

1. Three thin lenses in contact: biconvex glass ($n_1 = 1.5$) and two plano-concave liquid lenses ($n_2 = 1.6$), all with $R = 20\text{ cm}$.
2. Glass: $P_g = 0.5 \times \frac{2}{20} = \frac{1}{20}$; liquid: $P_l = -0.6 \times \frac{1}{20}$ each.
3. $P = \frac{1}{20} - \frac{1.2}{20} = -\frac{0.2}{20} = -\frac{1}{100}\text{ cm}^{-1}$
4. So the answer is (b) $-100\text{ cm}$.