A concave mirror is spherical and curves like a spoon and the curved surface has an inner surface that acts as the reflecting surface. Convex mirrors have an outer surface as the reflecting surface. The properties and images formed by a concave mirror are different from those of plane mirrors.
A concave mirror has two focal points, a center of curvature and a radius of curvature. The ray of light parallel to the principal axis passes through a focus point after reflection and forms the image. Images formed by a concave mirror may be diminished, magnified, real or virtual according to the position of the object.
Concave mirrors are used in telescopes and as shaving mirrors. They are also used to manufacture headlights of vehicles to get a parallel beam of light.