Describe an aspheric lens.

• A. A lens with constant curvature across its surface
• B. A lens whose radius of curvature gradually changes from the center outward towards the lens edge
• C. A lens with multiple surfaces only
• D. A lens with uniform thickness

Answer: (B)

An aspheric lens has surfaces whose curvature is not constant; the radius of curvature changes as you move from the center toward the edge. This variation in curvature reduces spherical aberration, giving sharper peripheral vision and allowing lenses to be thinner and lighter. That’s why the description fits best: a lens whose radius of curvature gradually changes from the center outward toward the lens edge. The other options describe spherical surfaces (constant curvature), require multiple surfaces by definition, or reference thickness rather than surface shape, none of which define an aspheric surface.