If you are viewing an object with a 7 Diopter lens and a 10 Diopter lens, which one has to be held closer to a piece of paper when focusing a distant object?
A) The 7 Diopter lens
B) The 10 Diopter lens
C) Both have the same focal length
D) Neither one will focus an image.

Question

Quizplus · Accepted Answer

The 10 Diopter lens has to be held closer to the paper because it has a shorter focal length. Diopter is inversely related to focal length (focal length = 1/Diopter), so a higher diopter means a shorter focal length.

If You Are Viewing an Object with a 7 Diopter