As light passes through a lens, its path is changed owing to refraction, causing light rays to bend. The curvature of the lens determines how much the light rays are bent. Convex and Concave are the two main categories of lenses.
The center of a convex lens sometimes referred to as a converging lens, is thicker than the borders. The focal point is where the light rays converge when they go through a convex lens. The focal length is defined as the distance between the center of the lens and the focal point. Often found in magnifying glasses, telescopes, and cameras are convex lenses.
The center of a concave lens often referred to as a diverging lens, is thinner than the borders. The light beams diverge, or widen apart, as they travel through a concave lens. A concave lens's focal point is where light rays appear to be originating from; it is situated behind the lens. Corrective eyewear and microscopes frequently employ concave lenses.