Question

what is the focal length of concave mirror and concave lens ____​

Answer 1

Explanation:

A distant object (at infinity) when reflected by a concave mirror, forms a real, diminished, and inverted image at the focus of the mirror. As the distance between the pole 0 of the concave mirror and the focus F is the focal length of the concave mirror.

Answer 2

Explanation:

Positive for Concave mirror.

Negative for Convex mirror.