Concave lens, showing the divergence of light rays. Diverging lenses have a virtual focus and make objects look smaller. Concave lenses diverge (spread apart) incoming light rays. If these rays are traced backward these imaginary lines converge to a point or virtual focus behind the lens. This is in contrast to convex (or converging lenses) which bring rays together in front of the lens to a real focus. Simulation of a concave lens changing its curvature.