A lens is an optical device that produces real images. Lenses are typically made of glass or plastic and have a curved surface. When light passes through a lens, it is refracted, or bent. This bending of light can cause the light to converge (come together) or diverge (spread out).

A converging lens is a lens that causes light to converge. This type of lens is thicker in the middle than at the edges. When light passes through a converging lens, it is refracted toward the center of the lens. This causes the light to come together at a point called the focal point. The focal point is located at a fixed distance behind the lens.

A diverging lens is a lens that causes light to diverge. This type of lens is thinner in the middle than at the edges. When light passes through a diverging lens, it is refracted away from the center of the lens. This causes the light to spread out as it passes through the lens.

Lenses are used in a variety of optical devices, including cameras, telescopes, and microscopes.