Q 12-09-121JEE MainJEE Main 2023 (12 Apr, Shift 1)Easy
Two convex lenses of focal length $20\ \text{cm}$ each are placed coaxially with a separation of $60\ \text{cm}$ between them. The image of the distant object formed by the combination is at ______ cm from the first lens.
Numerical value type. Enter your answer.
Answer: 100
The first lens forms the image at $20\ \text{cm}$, i.e. $40\ \text{cm}$ before the second lens. The second lens images it at $\dfrac1v=\dfrac1{20}-\dfrac1{40}\Rightarrow v=40\ \text{cm}$ beyond it.
Distance from the first lens $=60+40=100\ \text{cm}$.
Solution by Sreeraj P, M.Sc Physics