Question

define optic centre and focus of lens​

Answer 1

Answer:

optical center

: a point on the axis of a lens that is so located that any ray of light passing through it in passing through the lens suffers no net deviation and that may be within, without, or on either surface of the lens.

A principal focus or focal point is a special focus: For a lens, or a spherical or parabolic mirror, it is a point onto which collimated light parallel to the axis is focused. Since light can pass through a lens in either direction, a lens has two focal points – one on each side.