To construct a ray diagram, we use two light rays which are so chosen that it is easy to know their directions after reflection from the mirror. List these two rays and state the path of these rays after reflection. Use these rays to locate the image of an object placed between centre of curvature and focus of a concave mirror.
Rays which are chosen to construct ray diagram for reflection are:
(i) A ray parallel to the principal axis and
(ii) A ray passing through the centre of curvature of a concave mirror or appear to pass through the centre of curvature of convex mirror.
Path of these rays after reflections is:
(i) After reflection, the first ray will pass through the principal focus of a concave mirror or appear to diverge in case of a convex mirror.
(ii) After reflection, the second ray is reflected back along the same path.