Sign Conventions of Ray Diagrams

These new cartesian sign conventions adopted during measurements are as follows:

• All distances are measured from the pole of spherical mirrors.

• Distances measured in the direction of incidence of light are taken as positive, and when measured in a direction opposite to the direction of incidence of light is taken as negative.

• The heights measured upwards to the principal axis are taken as positive and negative if measured downwards.

Rules for Drawing Ray Diagrams

• Any ray of light traveling parallel to the principal axis, after reflection pass through the focus or appears to diverge from the focus.

Curvature Reflects

• Any ray of light passing through the centre of curvature reflects along the same path.

• A ray of light initially passing through the focus after reflection travels parallel to the principal axis.