Question

The cornea of the eye has a radius of curvature of approximately 0.50 cm, and the aqueous humour behind it has the index of refraction of 1.35. The thickness of the cornea itself is small enough that we shall neglect it. The depth of a typical human eye is around 25 mm.

(a)What would have to be the radius of curvature of the cornea so that it alone would focus the image of a distant mountain on the retina that is at the back of the eye opposite the cornea?

(b) If cornea focused the mountain correctly on the retina as described in part (a), would it also focus the text from a computer screen on the retina if that screen were 25 cm in front of the eye? If not, where will it focus that text: in front of or behind the retina?

(c) Known that cornea has a radius of curvature of about 5.0 mm, where does it actually focus the mountain? Is this in front of or behind the retina? Does this help you see why the eye needs help from a lens to complete the task of focusing?