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Question 20193
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Ray Optics: Focal Length of Concave Mirror MCQ

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Focal Length of Concave MirrorEasyQuestion 20193

Question

A concave mirror has radius of curvature 20 cm. Its focal length is:
  1. A
    20 cm
  2. B
    10 cm
    Correct
  3. C
    40 cm
  4. D
    5 cm

Correct answer

10 cm

Explanation

f = R/2 = 20/2 = 10 cm. For a concave mirror, f is negative (−10 cm) by convention.

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