Question

why focal length of a conave mirror is negative?​

Answer 1

Answer:

because images does not forms on front of the mirror and for back of mirror we use negative

Answer 2

Answer:

Check Explanation

Explanation:

In a concave mirror, the light rays from the object converge after reflection. Light rays from infinity, parallel to the principal axis, thus meet at the a point on the principal axis on the side of the mirror which is towards the object. This distance is considered as negative since it is on the side of the object.

So the focal length of a concave mirror is negative