Explain Cartesian sign convention in case of refraction through lens.

Explanation

Cartesian sign conventions for lens:


i. Optical centre (0) of a lens is taken as origin and principal axis oflens is taken as X-axis.
ii. All distances measured to the right of the origin are taken as positive, while distances measured to the left of the origin are taken as negative.
iii. Distances measured perpendicular to and above the principal axis are taken as positive.
iv. Distances measured perpendicular to and below the principal axis are taken as negative.