Question

Giving reasons, state the 'signs' (positive or negative) which can be given to the following:

(a) object distance (u) for a concave mirror or convex mirror
(b) image distance (v) for a concave mirror
(c) image distance (v) for a convex mirror

Answer 1

(a) Object distance (u) for a concave or convex mirror is given a negative sign. This is because, the object is always placed to the left of the mirror.
(b)

1. The image distance (v) for a concave mirror is given a positive sign if the image formed is behind the mirror and to the right of it.
2. The image distance (v) for a concave mirror is given a negative sign if the image formed is in front of the mirror and to the left of it.

(c) The image distance (v) for a convex mirror is always given a positive sign because the image is always formed behind the mirror and to the right of it.