Question

What is the sign convention of a concave mirror

Answer 1

Since, object is always placed in front of the mirror hence the sign of object is taken as negative. Since, the centre of curvature and focus lies behind the convex mirror, so sign of radius of curvature and focal length are taken as + (positive) in the case of convex mirror.

Answer 2

in the concave mirror....
the u is -ve becoz it lies in the left side of the mirror.the v is also +ve becoz the image is formed in right side of the mirror.and the f is -ve bcoz it lies in the left side of the mirror.