State the rules used for drawing ray diagrams for the fomation of an image by a convex lens .

Explanation

Rules used for drawing ray diagrams for the formation of an image by a convex lens :
(1) When the incident ray is parallel to the principal axis, the refracted ray passes through the principal focus.
(2) When the incident ray passes through the principal focus , the refracted ray is parallel to the principal axis.
(3) When the incident ray passes through the optical centre of the lens, it passes without changing its direction.