(a) The rays used for obtaining the image from the mirror after reflection are as follows:
1. A ray which is parallel to the principal axis which on reflecting from the mirror, passes through the focus (when the mirror is concave) or appears to pass through the focus (in case of convex mirror).
2. A ray which passes through the principal focus of the mirror is directed towards the principal focus , in case of convex mirror, it will emerge as parallel to the principal axis of the mirror.
3. The Ray which passes through the center of curvature of concave mirror or directed in the direction of center of curvature of convex mirror, reflects back along the same path.
(b) The ray diagrams are as follows:
1. When object is placed between infinity and C:
2. When the object is placed between pole and focus of a concave mirror
3. When the object is placed between pole and focus of convex lens: