The best method for formation of images by mirror is through ray tracing. The point at which reflected rays will intersect gives the location of images.
(a) A ray parallel to the axis, after reflection, passes through the focal point of a concave mirror or appears to come from the focal point of a convex mirror.
(b) A ray from (or proceeding towards) the focal point is reflected parallel to the axis.
(c) A ray along the centre of curvature intersects the surface normally and is reflected back along its original path.
(d) A ray incident to the pole is reflected with equal angles with the principal axis.
In any given situation, only two of these rays are sufficient to locate the image.