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 refraction 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.