Q 12-09-084JEE MainJEE Main 2024 (4 Apr, Shift 1)Easy
The effective power of a combination of 5 identical convex lenses which are kept in contact along the principal axis is $25\ \text{D}$. The focal length of each of the convex lenses is
Answer: (A) $20\ \text{cm}$
Powers add: $5P = 25\ \text{D} \Rightarrow P = 5\ \text{D}$, so $f = \dfrac{1}{5}\ \text{m} = 20\ \text{cm}$.
Solution by Sreeraj P, M.Sc Physics