Question:
The focal length of which mirror is taken as negative according to the convention of signs?
The focal length of which mirror is taken as negative according to the convention of signs?
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Remember: Concave = negative focal length, Convex = positive focal length.
Updated On: Oct 27, 2025
- Plane mirror
- Concave mirror
- Convex mirror
- None of these
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The Correct Option is B
Solution and Explanation
Step 1: Sign convention.
In mirror formula, distances measured against incident light are taken negative.
Step 2: Mirrors.
For concave mirror, focal length is on the left side (against light), hence negative.
For convex mirror, focal length is positive.
Step 3: Conclusion.
So, concave mirror has negative focal length.
In mirror formula, distances measured against incident light are taken negative.
Step 2: Mirrors.
For concave mirror, focal length is on the left side (against light), hence negative.
For convex mirror, focal length is positive.
Step 3: Conclusion.
So, concave mirror has negative focal length.
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