Using lens formula: $\frac{1}{v} - \frac{1}{u} = \frac{1}{f}$
$$\frac{1}{60} - \frac{1}{u} = \frac{1}{20}$$
$$\frac{1}{u} = \frac{1}{60} - \frac{1}{20} = -\frac{1}{30}$$
Object distance $= 30\,\text{cm}$
Back to JEE Main 2021 Optics
JEE Main 2021 — Physics Optics
easy
mcq
2021
Official previous-year question
Verified 30 May 2026.
Question
A convex lens of focal length $20\,\text{cm}$ forms an image at $60\,\text{cm}$ from the lens. The object distance is:
Options
- A
$30\,\text{cm}$
- B
$25\,\text{cm}$
- C
$20\,\text{cm}$
- D
$15\,\text{cm}$
Solution
Did you get this right?
Sign in to track your attempts and accuracy.
Your note
Sign in to keep a private note on this question. Nothing you write is ever public.
JEE Main Optics in other years
More JEE Main Optics Questions
In Young's double slit experiment, the fringe width is β. If the wavelength of light is doubled and the slit separation is halved, the new fringe width is:
2026
medium
mcq
The critical angle for total internal reflection from a medium to air is 30°...
2024
medium
mcq
The thin lens formula is:
2024
medium
mcq
In a single slit diffraction pattern the angular width of the central maximum is 0.1 rad...
2023
hard
mcq
A thin prism of angle 6° and refractive index 1.5 is combined with another prism of angle 4° and refractive index 1.75...
2022
medium
mcq