Sunlight reflected off a mirror you are holding is focused at a point 330 mm in front of the mirror.
What is the radius of curvature of the mirror?

Focal length of the mirror will be 660 mm          

Explanation:

We have given that sunlight is focused at a distance of 330 mm in front of mirror

So focal length f = 330 m

We have to find the radius of curvature

Radius of curvature is double the focal length

So radius of curvature = 2× focal length = 2×330 = 660 mm

So focal length of the mirror will be equal to 660 mm

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