Question

What is the Cartesian sign convention used for spherical mirrors?

Answer 1

According to the Cartesian sign convention, the pole (P) of a spherical mirror is considered as the origin, and the principal axis is taken as the X-axis of the coordinate system.

1. The object is always positioned on the left side of the mirror.
2. All distances measured parallel to the principal axis are taken from the pole of the mirror.
3. Distances measured to the right of the origin (pole) are considered positive, whereas distances measured to the left of the origin (pole) are considered negative.
4. Distances measured perpendicular to and above the principal axis are taken as positive.
5. Distances measured perpendicular to and below the principal axis are taken as negative.
6. The focal length of a convex mirror is positive, whereas the focal length of a concave mirror is negative.