Q 12-09-243JEE MainJEE Main 2025 (8 Apr, Shift 2)Easy
A convex lens of focal length $30\ \text{cm}$ is placed in contact with a concave lens of focal length $20\ \text{cm}$. An object is placed at $20\ \text{cm}$ to the left of this lens system. The distance of the image from the lens in cm is:
Answer: (D) $15$
$$\frac1F = \frac1{30} - \frac1{20} = -\frac1{60} \Rightarrow F = -60\ \text{cm}$$
With $u = -20\ \text{cm}$:
$$\frac1v = \frac1F + \frac1u = -\frac1{60} - \frac1{20} = -\frac4{60} \Rightarrow v = -15\ \text{cm}$$
The (virtual) image is $15\ \text{cm}$ from the lens, on the object's side.
Solution by Sreeraj P, M.Sc Physics