Question:
A convex lens of focal length \(0.12\,m\) produces an image which is three times the size of the object. The distance between the object and the lens for a real image is:
A convex lens of focal length \(0.12\,m\) produces an image which is three times the size of the object. The distance between the object and the lens for a real image is:
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For real image: magnification is negative.
Updated On: Apr 16, 2026
- \(0.16\,m\)
- \(-0.16\,m\)
- \(1.6\,m\)
- \(-1.6\,m\)
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The Correct Option is A
Solution and Explanation
Concept:
Magnification:
\[
m = \frac{v}{u}
\]
Lens formula:
\[
\frac{1}{f} = \frac{1}{v} + \frac{1}{u}
\]
Step 1: Given magnification.
\[ m = -3 \quad (\text{real image}) \Rightarrow v = -3u \]
Step 2: Substitute in lens formula.
\[ \frac{1}{f} = \frac{1}{-3u} + \frac{1}{u} = \frac{-1 + 3}{3u} = \frac{2}{3u} \] \[ \frac{1}{0.12} = \frac{2}{3u} \Rightarrow u = 0.16\,m \]
Step 1: Given magnification.
\[ m = -3 \quad (\text{real image}) \Rightarrow v = -3u \]
Step 2: Substitute in lens formula.
\[ \frac{1}{f} = \frac{1}{-3u} + \frac{1}{u} = \frac{-1 + 3}{3u} = \frac{2}{3u} \] \[ \frac{1}{0.12} = \frac{2}{3u} \Rightarrow u = 0.16\,m \]
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