Question

Write the rules for sign convention.

Answer 1

The measurement along the principal axis

always starts from C.

(a) From C, if you measure a distance in the direction of incident ray (towards right in this case), the measurement is taken positive.

(b) From C, if you measure a distance opposite to the direction of incident ray (towards left in this case), the measurement is taken negative.

(c) The height measured above the principal axis is taken as positive.

(d) The height measured below the principal axis is taken as negative.