WBJEE · Physics · Ray Optics
A convex lens of focal length \(30 \mathrm{~cm}\) produces 5 times magnified real image of an object. What is the object distance ?
- A \(36 \mathrm{~cm}\)
- B \(25 \mathrm{~cm}\)
- C \(30 \mathrm{~cm}\)
- D \(150 \mathrm{~cm}\)
Answer & Solution
Correct Answer
(A) \(36 \mathrm{~cm}\)
Step-by-step Solution
Detailed explanation
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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