Eyes: What power contact lens must be used to correct the vision of a nearsighted person whose far point is 40 cm?

Question

Quizplus · Accepted Answer

The power of a lens required to correct the vision of a person with myopia (nearsightedness) is negative. The formula to calculate the power of a lens is P=1/f, where P is the power in diopters and f is the focal length in meters. For a myopic person, the far point of their eye is closer than infinity, so we can assume the far point as the focal length.

far point = 40 cm = 0.4 m
P = 1/f = 1/0.4 = 2.5 diopters (negative, for myopia)

Therefore, the correct answer is B, -2.5 diopters.

Eyes: What Power Contact Lens Must Be Used to Correct