What is the focal length of the corrective contact lens needed by a nearsighted person whose far point is at 60 cm?
A) -60 cm
B) -30 cm
C) +60 cm
D) +30 cm
E) +130 cm

Question

Quizplus · Accepted Answer

The focal length of the corrective lens for a nearsighted person should allow them to see distant objects clearly. Since their far point is 60 cm, the lens needs to correct vision to infinity. The formula for lens power (P) is P = 1/f, where f is the focal length in meters. To correct to a far point of 60 cm (0.6 meters), the lens must have a focal length that brings parallel rays of light to focus at 60 cm. Thus, the focal length is -60 cm, indicating a diverging lens is needed. Negative because it corrects for nearsightedness by diverging light rays before they enter the eye.

What Is the Focal Length of the Corrective Contact Lens