Question

Concave mirror is a part of sphere of radius 40 cm. what is the focal length of the mirror?

Answer 1

Answer :

The focal length of the mirror is 20cm

Given :

Radius of curvature of the spherical mirror = 40cm

To find :

The focal length of the mirror

Solution :

We know that focal length of a mirror = 1/2 of Radius of curvature

Therefore,

Focal length = 1/2 x 40

=40/2

=20cm

Hence, the focal length of the mirror is 20cm.

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Answer 2

The radius of curvature and focal length have a relationship in which the radius of curvature is twice the focal length. To put it another way, focal length is equal to half the radius of curvature..

In this case, radius of curvature of the concave mirror is given as 40 cm. Hence, the focal length of the mirror is $\frac{40}{2} =20cm$

Hence, the focal length of the concave mirror is $20cm.$

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