The normal, human eye forms a real, diminished, inverted image on the retina.
Most of the refraction occurs at the air – cornea boundary.
Light then enters the lens after passing through the pupil.
The iris is the coloured part of the eye, surrounding the pupil.
The converging (convex) lens provides the rest of the refraction necessary to focus the rays of light sharply on the light sensitive cells of the retina at the back of the eye.
The ciliary muscles change the shape and hence the focal length of the lens, allowing the eye to focus on both near and far objects.