The paraxial (close to axis) beam of light is parallel to the axis, after reflection
converges at F; when the Laws of reflection are applied to small parts at M
and N, they are considered as flat or plane surfaces.
Image formation in concave mirror
The ray diagram will be drawn as follows :
(i) A ray incident and parallel to axis will reflect through
(ii) A ray incident through focus will reflect parallel to the axis.
(iii) A ray incident through center of curvature will reflect backwards along the same path.