To construct ray diagrams, two rays of light are generally so chosen that it is easy to determine their directions after reflection from a mirror. Choose two such rays and state the path/direction of these rays after reflection from a concave mirror. Use these two rays to find the position and nature of the image of an object placed at a distance of 8 cm from a concave mirror of focal length 12 cm.

The candidate may choose any two of the following rays:
(i) A ray parallel to the principal axis, after reflection, will pass through the principal focus
of a concave mirror.
(ii) A ray passing through the principal focus of a concave mirror after reflection will emerge
parallel to the principal axis.
(iii) A ray passing through the center of curvature of a concave mirror after reflection is
reflected back along the same path.
(iv) A ray incident obliquely to the principal axis towards the pole of a concave mirror is reflected obliquely; making equal angles with the principal axis

Using the ray number (iii) and (iv) we can draw the required ray diagram.