Question

why spherical lens has two focus?

Answer 1

Hey mate here is your answer》》

The reason why a lens has two focii while a mirror has only one is because of the fact that light is transmitted through a lens and not a mirror. Unlike in mirrors, images in lenses can form on either side and thus we require two focii to properly determine the formation and position of an image.

Hope this answer will help you..《《

Answer 2

Y because focal length will focus the convex and concave lengths