A nearsighted person has a far point of 33 cm. What focal length contact lens would allow her to see in the distance?
A) 33 cm
B) −33 cm
C) 67 cm
D) −67 cm
E) 3.0 m

Question

Quizplus · Accepted Answer

For a nearsighted person to see distant objects clearly, the far point of their vision must be corrected to infinity. The lens formula 1/f = 1/v - 1/u can be used, where f is the focal length of the lens, v is the image distance (considered infinity for distant objects), and u is the object distance (the far point of the person, which is -33 cm, negative because it is on the same side of the lens as the light is coming from). Solving for f gives us -33 cm, indicating a diverging lens is needed with a focal length of -33 cm.

A Nearsighted Person Has a Far Point of 33 Cm