The radius of curvature of a spherical mirror is 20 cm. What is its focal length?

20 cm

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10 cm

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30 cm

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40 cm

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Solution

The correct option is B
10 cm

Radius of curvature, R = 20 cm
Radius of curvature of a spherical mirror = 2 $\times$ Focal length (f)
R = 2f
$f = \frac{R}{2} = \frac{20}{2} = 10$
Hence, the focal length of the given spherical mirror is 10 cm.

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