Question

A farsighted person has a near point of 40 cm.

What strength lens, in diopters, is needed to bring his near point to 25 cm ?

Answer 1

To find the strength of the lens needed to bring the near point to 25 cm for a farsighted person, use the lens formula.

Step-by-step explanation:

To find the strength of the lens needed to bring the near point to 25 cm for a farsighted person, we can use the lens formula:

1/f = 1/v - 1/u

Where f is the focal length of the lens, v is the image distance, and u is the object distance.

Given that the near point is 40 cm, we can plug in the values:

1/f = 1/25 - 1/40

Simplifying this equation, we find that the lens strength, or focal length, is -40 cm, or -2.5 diopters.