Which lens is thinner in the center than at the edges?

Which lens is thinner in the center than at the edges?

• A. Glass slab
• B. Concave lens
• C. Prism
• D. Convex lens

Answer: (B)

The shape of a lens determines how thick it is at the center compared with the edges, which in turn affects how it bends light. A concave lens has inward-curved surfaces, making the center the thinnest part. That thinner center is what gives it the ability to diverge light rays, spreading them apart as they pass through. In contrast, a convex lens bulges outward and is thickest at the middle, causing light to converge. A glass slab has flat faces, so its thickness is the same all the way across, and a prism is a wedge-shaped piece, not a symmetric lens whose center is thinner than the edges. So the lens that is thinner in the center than at the edges is the concave lens.

The shape of a lens determines how thick it is at the center compared with the edges, which in turn affects how it bends light. A concave lens has inward-curved surfaces, making the center the thinnest part. That thinner center is what gives it the ability to diverge light rays, spreading them apart as they pass through. In contrast, a convex lens bulges outward and is thickest at the middle, causing light to converge. A glass slab has flat faces, so its thickness is the same all the way across, and a prism is a wedge-shaped piece, not a symmetric lens whose center is thinner than the edges. So the lens that is thinner in the center than at the edges is the concave lens.