What is the focal length (in cm) of a concave mirror whose radius of curvature is ?
Answer and explanation
Correct answer: D. 20
- Step 1: For a spherical mirror of small aperture, the focal length is related to its radius of curvature by the formula .
- Step 2: Substitute the radius of curvature : .
Answer
20.
Why not the others: is the radius of curvature ; divides by 4; and doubles instead of halving it.
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