Question Detail
Question
A 15-year-old boy requires eyeglasses with a power of 2 diopters to read a book at 25 cm. What is the focal length of these eyeglasses?
Correct Answer
Option B is the correct answer.
Detailed Explanation
The power of a lens (P) is the reciprocal of its focal length (f) in meters (P = 1/f). Given P = +2 diopters, f = 1/P = 1/2 m = 0.5 meters, which is 50 cm.
Hint
Remember the relationship between lens power and focal length, and the required units for focal length when calculating power.