Question

The uncorrected eye. For the following questions, assume that the distance between the eye lens and the retina is 1.70 cm. In other words, since the image is always formed on the retina, the distance between the lens and the image is always 1.70 cm. Also note that, as is seen in the ray diagram, since the eye lens is converging and the image is on the opposite side of the lens compared to the object, the image is always real.

One nearsighted patient has a far point of 400 cm. What is the focal length of her eye when an object is at her far point?

Answer 1

object is at far point means object distance, do = 400 cm

image distance, di = 1.7 cm

so,

using lens equation

1/f = 1/do + 1/di

1/f = 1/400 + 1/1.7

f = 1.692 cm