A lens that is thinner in the center than at the edges

• A. Convex Lens
• B. Plano Lens
• C. Biconcave Lens
• D. Concave Lens

Answer: (D)

Being thinner in the center means the lens surfaces curve inward toward the center, making the central region the thinnest part. That shape is a concave lens. Concave lenses diverge light, bending rays outward so they spread apart as if they came from a point on the same side as the object, and they have a negative focal length. The edges are thicker than the center, which matches the description. Convex lenses bulge in the middle and are thicker there, plano lenses have a flat surface on one side, and while a biconcave lens also has a thinner center, the term that most directly describes a lens thinner at the center is concave.