Sign Convention of Lens
Sign Convention of Lens :- Sign convention is a set of rules to set signs for image distance (u), object distance (v), focal length (f), etc. for mathematical analysis of image formation. According to it :-
- Object is always placed to the left of lens.
- All distances are measured from the optical center of the lens.
- Distances measured in the direction of the incident ray are positive and the distances measured in the direction opposite to that of the incident rays are negative.
- Distances measured along y-axis above the principal axis are positive and that measured along y-axis below the principal axis are negative.
- Sign convention can be reversed and will still give the correct results.
- Convex lens has positive focal length and concave lens has negative focal length.