A person's near point is 25 cm,and her eye lens is 2.7 cm away from the retina.What must be the focal length of this lens for an object at the near point of the eye to focus on the retina?
A)-3.4 cm
B)-2.4 cm
C)2.4 cm
D)3.4 cm
E)2.6 cm

Question

Quizplus · Accepted Answer

The lens formula is 1/f = 1/v - 1/u, where v is the image distance (2.7 cm) and u is the object distance (-25 cm, since it's a virtual object for the eye). Solving gives f = 2.4 cm.

A Person's near Point Is 25 Cm,and Her Eye Lens