Which lens type is thicker in the middle than at the edges?

A convex lens is characterized by being thicker in the middle than at the edges. This design allows it to converge light rays that are coming in parallel to its principal axis. When light passes through a convex lens, it bends towards the center, coming to a focal point on the opposite side. This feature makes convex lenses ideal for magnifying objects, focusing images, and correcting vision problems like hyperopia (farsightedness).

In contrast, a concave lens is thinner in the middle and thicker at the edges, causing light rays to diverge. A flat lens lacks curvature, thus not modifying the light path significantly, while a cylindrical lens has curvature in one direction only, affecting focus differently. The design of each type of lens directly impacts how they interact with light, which is why the thickness and shape of a convex lens are crucial for its function in optics.