What power lens is needed to correct for farsightedness where the uncorrected near point is 75 cm?
A) +2.67 D
B) +1.00 D
C) +5.33 D
D) -2.67 D
E) -5.33 D

Question

Quizplus · Accepted Answer

The lens power needed to correct farsightedness (hyperopia) can be calculated using the formula P = 1/f, where P is the power in diopters (D) and f is the focal length in meters. The near point of 75 cm (0.75 m) indicates the closest point at which the eye can focus on an object. To correct this, a converging lens is needed with a focal length equal to the near point distance, so P = 1/0.75 = 1.33 D. However, since the standard near point is considered to be 25 cm (0.25 m), and the person's near point is 75 cm, the calculation should actually consider the difference needed to bring the near point from 75 cm to 25 cm. Thus, the correct calculation is P = 1/0.25 = 4 D, indicating a need for a lens that brings objects at 25 cm into focus. The initial calculation provided was incorrect; the correct approach to find the power of the lens involves considering the adjustment needed to correct the vision to a normal near point, which wasn't accurately reflected in the initial explanation.

What Power Lens Is Needed to Correct for Farsightedness Where