The near point of a farsighted person is 100 cm.She places reading glasses very close to her eyes,and with them she can comfortably read a book at a distance of 25 cm.What is the power of the lenses in her reading glasses?
A)+2.5 diopters
B)+3.0 diopters
C)+3.2 diopters
D)-2.0 diopters

Question

Quizplus · Accepted Answer

The near point of a farsighted person is farther away than the typical 25 cm. This means that the person has a positive refractive error as the focus of the light entering the eye is behind the retina. The reading glasses of a farsighted person have a positive power to converge the light rays entering the eye.

To calculate the power of the reading glasses, we can use the formula:

P = 1/f

Where P is the power of the lenses in diopters and f is the focal length of the lenses in meters.

The near point of the person is 100 cm, which is the far point of the eye when reading glasses are not used. Therefore, the person needs the lenses to focus light entering the eye as if it were coming from 25 cm away:

1/f = 1/25 - 1/100 = 3/100

f = 100/3 cm = 33.3 cm

P = 1/f = 3 diopters = +3.0 diopters

Therefore, the correct answer is B.

The near Point of a Farsighted Person Is 100 Cm