Light rays entering a converging lens parallel to its axis cross one another at a single point on the opposite side. For a converging lens, the focal point is the point at which converging light rays ...Light rays entering a converging lens parallel to its axis cross one another at a single point on the opposite side. For a converging lens, the focal point is the point at which converging light rays cross; for a diverging lens, the focal point is the point from which diverging light rays appear to originate. The distance from the center of the lens to its focal point is called the focal length \(f\). Power \(P\) of a lens is defined to be the inverse of its focal length, \(P = \frac{1}{f}\).
