A parallel beam of light is incident on a converging lens parallel to its principal axis. As one moves away from the lens on the other side on its principal axis, the intensity of light

The converging lens's focus is where the parallel light beams converge. The intensity rises as the rays converge just before they reach the focal. At the focus, the intensity is at its highest. When the beams focus, they begin to part. As a result, the intensity drops even more.