Question

Define the principal focus of a concave lens

Answer 1

${\mathfrak{\red{\underline{\underline{Answer:-}}}}}$

Principal focus of a convex lens is the point on the principal axis where rays incident parallel to the principal axis will pass through that point after getting refracted by the lens. In the fig. F denotes the principal focus of the lens.

Principal focus of a concave lens is the point on the principal axis where rays incident parallel to the principal axis will appear to diverge from that point when produced behind the lens, after getting refracted by the lens.  In the fig. F denotes the principal focus of the lens.

Answer 2

When parallel rays of light pass through a convex lens the refracted rays converge at one point called the principal focus. The distance between the principal focus and the centre of the lens is called the focal length.

brainliest plz _/\_