Write the rules for sign convention. (AS1)

The sign conventions which are used while studying positions of object & image differs from books to books. But most commonly, Cartesian sign conventions are used. The pole is taken as a reference point. The rules for sign conventions are:

• The diagrams are drawn with the incident light travelling from left to right.

• The distances are measured by taking pole as the origin.

• The distances measured in the direction of incident light are taken positive while those measured in the direction opposite to it are taken as negative.

• Heights measured upward and perpendicular to the principal axis are taken as positive while those measured downwards are negative.

• Angles measured clockwise with optic axis as reference are negative and angles measured anti-clockwise as positive.