Question

Calculate the focal length of a concave mirror if its radius of curvature is 12cm ​

Answer 1

Answer:

focal length f of concave mirror = 1/2 of radius of curvature = 12/2 = 6 cm .

Answer 2

Answer:

The focal length of a concave mirror if its radius of curvature is 12cm  will be $6\ cm$

Explanation:

• The distance from the pole to the center of curvature of the mirror is called the radius of curvature and focal length is the distance between the pole of the mirror and the focus of the object.

• Let R be the radius of curvature and f be the focal length then,

       $R = 2f$    

   Or,  

        $f = \frac{R}{2}$     ...(1)

• That is, for spherical mirrors having a small aperture, the focal length is half of the radius of curvature.

In the question, it is given that,

$R = 12\ cm = 12\times 10^{-2} m$

Substitute  the value of 'f' into equation(1),

$f = \frac{12\times10^{-2}}{2} =6\times10^{-2} \ m = 6\ cm$