Question

why is the focal length of concave lens taken as negative​

Answer 1

Answer:-

A concave lens diverges the rays incident on it. So the image will be formed behind the lens. ... you can easily verify that the focal length is in the positive x direction for a convex lens while it is along the negative x direction for a concave lens. So f is positive for a convex lens and negative for a concave lens.

Answer 2

Explanation:

Kyuki vo right side mai form krta h image ko