Question
State the new cartesian sign convention followed for refraction of light through spherical lenses.
Solution
According to the new cartesian sign convention for refraction of light through spherical lenses:
Fig. New cartesian sign convention for a lens
(i) All distances are measured from the optical centre of the lens.
(ii) The distances which are measured in the same direction as that of the incident light are taken positive.
(iii) The distances measured, in the direction opposite to the direction of incident light are taken negative.
(iv) Distances measured upwards and perpendicular to the principal axis are taken as positive.
(v) Distances measured downwards and perpendicular to the principal axis are taken negative.
