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JEE MAIN 2025
08-04-2025 S2
Question
A convex lens of focal length 30 cm is placed in contact with a concave lens of focal length 20 cm. An object is placed at 20 cm to the left of this lens system. The distance of the image from the lens in cm is _________.
Select the correct option:
A
30
B
45
C
15
D
$\frac{60}{7}$
✓ Correct! Well done.
✗ Incorrect. Try again or view the solution.
Solution
Equivalent focal length $$ \begin{aligned} & \frac{1}{\mathrm{f}}=\frac{1}{\mathrm{f}_1}+\frac{1}{\mathrm{f}_2} \\ & =\frac{1}{30}+\frac{1}{-20}=\frac{2-3}{60}=-\frac{1}{60} \\ & \mathrm{f}=-60 \mathrm{~cm} \end{aligned} $$ Lens formula $$ \begin{aligned} & \frac{1}{v}-\frac{1}{u}=\frac{1}{f} \\ & \frac{1}{v}-\frac{1}{-20}=\frac{1}{-60} \\ & v=-15 \mathrm{~cm} \end{aligned} $$
Question Tags
JEE Main
Physics
Medium
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