Which type of lens would be described as convex?

A convex lens is characterized by its outward curvature, which means it bulges outward. This shape allows the lens to converge light rays that are passing through it, focusing them to a point on the opposite side of the lens. This property makes convex lenses useful in applications such as magnifying glasses, eyeglasses for farsightedness, and camera lenses.

The other descriptors do not accurately represent a convex lens. A lens that curves inward would be concave, while a completely flat lens would not have the ability to focus light in the same way. While being thin at the center may describe certain types of lenses, it specifically does not define a convex lens, as the thickness can vary depending on the degree of curvature. Thus, the correct identification of a convex lens is its outward curve, which is fundamental to its function in optics.