How does a camera lens focus light into an image?

A camera lens focuses light by bending rays through curved glass elements so they converge at a single point on the sensor or film. When light passes through a convex lens, it refracts, with rays from a distant point bending inward to meet at the focal point behind the lens. The distance between the lens and that convergence point is the focal length. To focus on subjects at different distances, the lens moves closer to or farther from the sensor. Objects at the focused distance produce sharp convergence points on the sensor, while objects at other distances produce overlapping circles of light, causing blur. Multiple lens elements are used in modern cameras to correct distortions and aberrations that a single piece of glass would introduce.