What does a diopter measure?

• A. Angle of view
• B. Magnification
• C. Light intensity
• D. Color temperature

Answer: (B)

Diopter quantifies the refractive power of a lens. It is defined as the reciprocal of the focal length in meters, so higher diopter values mean a lens has stronger bending power and a shorter focal length. This stronger power enables greater angular magnification when viewing near objects, which is why the diopter is tied to how much a lens can magnify. The other options relate to field of view, brightness, or color, not to the lens’s magnifying ability.