Question

The focal length of a mirror is the

• A. Distance of the focus from the centre
• B. Half the radius of curvature.
• C. Distance of the focus from the pole
• D. Distance of the centre from the pole

Answer 1

Answer: (A), (B), (C)

The correct options are
A

Distance of the focus from the centre

B

Half the radius of curvature.

C

Distance of the focus from the pole

The focal length of a mirror is the distance from the pole to the focus but if you look at it mathematically it is also half of the radius (r=2f) so it is also equal to the distance from the centre to focus.