Question

State the principles of image formation in the case Of a spherical mirror. Use this principle to describe with the help of a diagram the nature, size, and position of the image formed when an object is placed beyond the centre Of curvature of a concave mirror.

Answer 1

Rules for reflection of light from a concave mirror:

1. A ray incident parallel to the principal axis passes through the principal focus after reflection.
2. An incident ray passing through the centre of curvature is reflected back along the same path.
3. A ray of light incident at the pole of a concave mirror and makes an angle (O) with its principal axis is reflected back making the same angle (6) with the principal axis.
4. An incident ray passing through the principal focus of the mirror becomes parallel to its principal axis after reflection.

Ray diagram to describe the nature, size, and position of the image formed when an object is placed beyond the centre of curvature of a concave mirror:

1. The above Fig. shows an object PQ placed beyond the centre of curvature of the mirror.
2. Ray 1 is an incident ray parallel to the principal axis starting from point Q of the object.
3. The reflected ray 1' passes through the focus F. Ray 2 is a second ray starting from Q and passes through F.
4. The reflected ray 2' is parallel to the principal axis. The two reflected rays I' and 2' meet at point Q'.
5. Clearly Q' is the image of point Q on the object. Obviously, P'Q' is the image of the object PQ.
6. The image formed between C and F is real, inverted, and diminished in size as shown in Fig.