Question

what is focal length ? explain with concave lens​

Answer 1

Explanation:

Definition: Focal length. Focal length. Focal length (shown in red) is the distance between the center of a convex lens or a concave mirror and the focal point of the lens or mirror — the point where parallel rays of light meet, or converge.

Answer 2

Answer:

The distance from the lens to the focal point is called the focal length. For converging lenses, the focal length is always positive, while diverging lenses always have negative focal lengths.