What is the primary characteristic of a concave lens?

A concave lens is primarily characterized by being thicker at the edges than in the middle. This design causes the lens to diverge light rays that pass through it. When parallel light rays enter a concave lens, they are spread out or diverged, making it appear as if they originate from a single point called the focal point on the same side of the lens from which the light comes.

This diverging property is a fundamental aspect of concave lenses and is why they are commonly used in applications such as corrective eyewear for nearsightedness, where they help the eyes to focus light properly on the retina.

The other choices pertain to properties that do not align with the characteristics of a concave lens. For instance, a lens that is thicker in the middle than at the edges describes a convex lens, which converges light rather than diverging it. Similarly, a reflective surface pertains more to mirrors rather than lenses, and the convergence of light rays is associated with convex lenses rather than concave ones. Hence, the defining characteristic of a concave lens is its thickness at the edges compared to the middle.