Question

Why the focal length of concave lens is taken as negative and convex lens is taken as positive​

Answer 1

A concave lens diverges the rays incident on it. So the image will be formed behind the lens. So the image distance becomes negative. 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.

Answer 2

Answer:

A concave lens diverges the rays incident on it. So the image will be formed behind the lens. So the image distance becomes negative. 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.

hope this helps u ✌️

20ᴛʜᴀɴᴋꜱ+ꜰᴏʟʟᴏᴡ= ɪɴʙᴏx