Question Detail
Question
A person with hyperopia has a near point of 75 cm. To clearly read a book held at 30 cm from their eye, what focal length lens is required?
Correct Answer
Option B is the correct answer.
Detailed Explanation
For an object at u = 30 cm, the corrective lens must form a virtual image at the eye's near point, so v = -75 cm. Using the lens formula 1/f = 1/u + 1/v: 1/f = 1/30 + 1/(-75) = 1/30 - 1/75. Finding a common denominator (150): 1/f = (5/150) - (2/150) = 3/150 = 1/50. Thus, f = +50 cm.
Hint
The lens needs to create a virtual image of the object at the person's natural near point.