Rationalised 2023-24
Ray Optics and
Optical Instruments
247
3 Cartesian sign convention: Distances measured in the same direction
as the incident light are positive; those measured in the opposite
direction are negative All distances are measured from the pole/optic
centre of the mirror/lens on the principal axis The heights measured
upwards above x-axis and normal to the principal axis of the mirror/
lens are taken as positive