Your eye diameter 25 cm is able to focus the image of a tree

Your eye (diameter 2.5 cm) is able to focus the image of a tree on your retina. The tree is 28 m tall and 70 m away. What is the size of the image of the tree on your retina? (Be careful about the sign of the image size.)

Solution

image distance, di = 2.5 cm

di = 0.025 m

object distance, do = 70 m

height of tree, hi = 28 m

let the height is hi

as hi/ho = -di/do

hi/28 = -0.025/70

hi = 0.01 m

hi = 10 mm