Magnification = object distance/focal length

Among them, the object distance refers to the distance from the object to the eye, and the focal length refers to the focal length of reading glasses.

For +5.00D reading glasses, the reciprocal of focal length (f) can be expressed as +5.00. Suppose we calculate the magnification when the object distance is 13.3cm:

Magnification = 13.3cm/(+5.00) = 2.66 times.

Similarly, suppose we calculate the magnification of an object at a distance of 20 cm:

Magnification = 20cm/(+5.00) = 4x.

Therefore, when looking at objects at 13.3cm, the reading glasses will be enlarged by about 2.66 times. When you look at an object at 20cm, the reading glasses will be enlarged by about 4 times.