Refraction. Computer artwork showing light beams passing through a biconvex, or converging, lens. Refraction is the change of direction of a wave when it passes from one medium to another. The change in medium causes a change in speed and wavelength. The lens's converging power increases as the curvature increases. The point at which the rays cross is the focus (focal point of the lens). Converging lenses have a real focus and make objects look larger. They are used in magnifying glasses, binoculars, telescopes and microscopes.