Question:
A convex lens having power \(P\) is cut into two halves perpendicular to the principal axis. Then the power of each piece is
A convex lens having power \(P\) is cut into two halves perpendicular to the principal axis. Then the power of each piece is
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Cut perpendicular to axis → focal length doubles → power halves.
Updated On: Apr 24, 2026
- \(P\)
- \(\frac{P}{2}\)
- \(2P\)
- \(\frac{P}{4}\)
- \(4P\)
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The Correct Option is B
Solution and Explanation
Concept:
Power of lens:
\[
P = \frac{1}{f}
\]
Step 1: Effect of cutting.
Cutting perpendicular to principal axis increases focal length.
Step 2: New focal length.
\[ f' = 2f \]
Step 3: New power.
\[ P' = \frac{1}{2f} = \frac{P}{2} \]
Step 1: Effect of cutting.
Cutting perpendicular to principal axis increases focal length.
Step 2: New focal length.
\[ f' = 2f \]
Step 3: New power.
\[ P' = \frac{1}{2f} = \frac{P}{2} \]
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