Question

Q.. HOW DOES SIGN CONVENTION FOR LENSES AND MIRROR DIFFERS ?

Answer 1

The sign convention is based on the direction of light. For easy understanding it revolves around the XY coordinate system as long as direction of light is from left to right. All measurements are taken starting from the origin.

Distance measured -

1. Above x-axis is positive ; below x-axis is negative.

[virtual image is erect = above axis = positive; real image is inverted = below axis = negative]

2. For y-axis, right of origin is positive ; left of origin is negative.

[By convention, object distance is always negative.]



JUST FOLLOW THESE FOR BOTH
THERE IS NO DIFFERENCE THEN
BY APPLYING THESE CONVENTIONS SUBSTITUTE EACH VALUES TO THE MIRROR OR LENS EQUATION.