Without glasses, a person can comfortably read a magazine when it is held at $60 \mathrm {~cm}$ from his eyes. What should be the focal length of his contact lenses to allow him to read the magazine comfortably at a distance of $30 \mathrm {~cm}$ ?
A) $+ 60 \mathrm {~cm}$
B) $- 30 \mathrm {~cm}$
C) $+ 90 \mathrm {~cm}$
D) $+ 30 \mathrm {~cm}$
E) $- 60 \mathrm {~cm}$

Question

Quizplus · Accepted Answer

The focal length of the contact lenses should be equal to the distance between the magazine and the person's eyes when the magazine is held at a comfortable reading distance. In this case, the comfortable reading distance is 30 cm, so the focal length of the contact lenses should be +30 cm.

Without Glasses, a Person Can Comfortably Read a Magazine When 60 cm60 \mathrm {~cm}60 cm

Without Glasses, a Person Can Comfortably Read a Magazine When $60 \mathrm {~cm}$