A nearsighted person has a far point that is 4.2 m from his eyes.What focal length lenses must he use in his contact lenses to allow him to focus on very distant mountains?
A)-4.2 m
B)4.2 m
C)-5.2 m
D)5.2 m
E)-4.8 m

Question

Quizplus · Accepted Answer

The correct focal length for the lenses is -4.2 m. This is because a nearsighted person needs diverging lenses to correct their vision, which have a negative focal length. The far point distance indicates the maximum distance at which the person can see clearly without correction. To see distant objects clearly, the lenses must have a focal length that effectively extends this far point to infinity, which is achieved with a focal length that matches the negative of the far point distance.

A Nearsighted Person Has a Far Point That Is 4