Question

A person’s eye has a diameter of 2.5 cm and a converging lens that produces a clear, real image on the retina. When viewing an apple, the eye’s lens has a focal length of 2.4 cm. What is the distance between the apple and the person’s eye?

Answer 1

distance between apple and the eye of the person, u = 60 cm

Given:

image distance, u' = 2.5 cm

focal length, f = 2.4 cm

Solution:

By using lens maker formula:

`(1)/(f) = (1)/(u) + (1)/(u')`

where

u = object distance

u' = image distance

f = focal length

Putting the respective values in the lens maker formula:

`(1)/(2.4) = (1)/(u) + (1)/(2.5)`

`(1)/(u) = (1)/(2.4) - (1)/(2.5)`

`(1)/(u) = (2.5 - 2.4)/(2.4* 2.5)`

`(1)/(u) = 0.01667`

u = 60 cm