A concave lens is a type of lens that is thinner in the center than at the edges. It diverges light rays that pass through it, causing them to spread out. This property makes concave lenses useful in various applications, such as in eyeglasses for people who are nearsighted, helping them see distant objects more clearly. When light enters a concave lens, it appears to come from a point behind the lens, known as the focal point. This effect is why concave lenses are also used in devices like cameras and projectors, where controlling light direction is essential for clear images.