What type of lens is characterized as being thicker around the edges?

The lens characterized as being thicker around the edges is indeed a concave lens. A concave lens is designed to diverge light rays that are coming into it, causing them to spread out. This is achieved by having a surface that is curved inward, which results in the edges being thicker compared to the center.

Concave lenses are commonly used in various applications, such as correcting nearsightedness (myopia), where they help to focus images correctly on the retina. The diverging nature of these lenses allows them to create virtual images that appear closer to the eye.

In contrast, a convex lens, which is thicker at the center, converges light rays and is used to correct farsightedness (hyperopia). A bifocal lens features both concave and convex sections to correct for multiple vision issues in one lens, and flat lenses simply have no curvature, providing no optical power. Understanding the structure and function of these different types of lenses is crucial for their application in corrective eyewear.