A person cannot see clearly objects more than 70.0 cm away.What power of corrective lens should be prescribed if the glass is to be worn 1.00 cm in front of the eye?
A)1.45 diopters
B)-1.45 diopters
C)0.0145 diopters
D)-0.0145 diopters

Question

Quizplus · Accepted Answer

We know that the far point of the person's eye is at 70 cm. This means that his/her near point is at 1/f = 1/70cm, which is approximately 1.43 diopters. 
Since the corrective lens should be worn 1 cm in front of the eye, we need to add this distance to the focal length of the lens. So, 
1/f' = 1/f - 1/d
where d = 1 cm and f is the focal length of the corrective lens. Solving for f', we get 
f' = -1.45 diopters 
Therefore, the power of the corrective lens that should be prescribed is -1.45 diopters, which is answer choice B.

A Person Cannot See Clearly Objects More Than 70