The concave mirror is the inside of the spherical surface is the reflecting surface.
The characteristic of concave mirror to collect of rays or CONVERGEN
The cut point of focusing reflected rays mentioned FOCUS LENGTH
DEFINING OF CONCAVE MIRROR
The parts of concave mirror F C V C = center of mirror curve or radius of curvature F =the mirror focal point or focal length V = the mirror vertex FV = the distance of mirror focal length CV= the mirror radius