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Question: Answered & Verified by Expert
A convex lens of focal length \(30 \mathrm{~cm}\) produces 5 times magnified real image of an object. What is the object distance ?
PhysicsRay OpticsWBJEEWBJEE 2011
Options:
  • A \(36 \mathrm{~cm}\)
  • B \(25 \mathrm{~cm}\)
  • C \(30 \mathrm{~cm}\)
  • D \(150 \mathrm{~cm}\)
Solution:
2760 Upvotes Verified Answer
The correct answer is: \(36 \mathrm{~cm}\)
Hints: \(\frac{1}{5 \mathrm{u}}-\left(\frac{1}{-\mathrm{u}}\right)=\frac{1}{30}\)
\(\begin{aligned}
& \frac{1}{5 \mathrm{u}}+\frac{1}{\mathrm{u}}=\frac{1}{30}, \frac{5+1}{5 \mathrm{u}}=\frac{1}{30} \\
& \mathrm{u}=36 \mathrm{~cm} .
\end{aligned}\)

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