A decrease in the base curve diopter leads to a radius that is

A decrease in the base curve diopter leads to a radius that is

• A. Radius increases
• B. Radius decreases
• C. Radius stays the same
• D. Cannot determine

Answer: (A)

The key idea is that diopters and radius of curvature are inversely related. The base curve diopter is a measure of how curved the lens back surface is, and in optics the radius of curvature is the reciprocal of the diopter value (in meters): R = 1/D. So if the base curve diopter decreases, the radius must increase, yielding a flatter curve. For example, lowering from 50 D to 40 D changes the radius from 0.02 m to 0.025 m. Thus the radius increases when the base curve diopter decreases.

The key idea is that diopters and radius of curvature are inversely related. The base curve diopter is a measure of how curved the lens back surface is, and in optics the radius of curvature is the reciprocal of the diopter value (in meters): R = 1/D. So if the base curve diopter decreases, the radius must increase, yielding a flatter curve. For example, lowering from 50 D to 40 D changes the radius from 0.02 m to 0.025 m. Thus the radius increases when the base curve diopter decreases.