Question

why the focal length of concave mirrors is positive ​

Answer 1

Answer:

By convention, distances are measured, along the central axis, as positive from the mirror in the direction of the object and negative away from the object. Hence the radius of curvature and the focal length are positive for concave mirrors and negative for convex mirrors.

Answer 2

Answer:

by convention,distances are measured,a long the central axis,a s positive from the mirror in the direction of the object and negative away from the object.hence the radius of curvature and the focal length are positive for concave mirrors and negative foe convex mirror