What type of lens is thicker in the center and thinner at the edges, causing light rays to converge?

A convex lens is characterized by being thicker in the center and thinner at the edges. This shape causes light rays to converge as they pass through the lens. When parallel light rays strike a convex lens, they are bent inward towards a focal point on the opposite side of the lens, which is a key feature utilized in various optical devices like glasses, cameras, and magnifying glasses.

In contrast, a concave lens is thicker at the edges and thinner in the center, causing it to diverge light rays instead of converging them. A flat lens does not alter the path of light rays significantly, and a plano-convex lens has one flat surface and one convex surface, which can focus light but does not change the fundamental characteristic of being a convex lens. Hence, the defining feature of the convex lens as one that converges light makes it the correct choice.