Write laws of refraction for spherical lenses.

● The rays parallel to principal axis passes from principal focus after refraction. When this parallel incident ray falls on the concave lens they diverge back after refraction. When they are extended backward they seem to be meeting at focus.

● A ray of light passing through a principal focus after refraction from a convex lens will emerge parallel to the principal axis. A ray of light appearing to meet at the principal focus of a concave lens, after the refraction will emerge parallel to the principal axis.

● A ray of light passing through the optical center of a lens will emerge without any deviation.