A person's eye lens is 2.7 cm away from the retina. What must the focal length of this lens be in order for an object placed at the near point (N = 25.0 cm) 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. Here, v = 2.7 cm (distance from lens to retina) and u = -25 cm (object distance, negative as per sign convention). Solving gives f = 2.4 cm.

A Person's Eye Lens Is 2