Describe the structure of human eye ?

Explanation

1) The eye ball is nearly spherical in shape. The frnt portion is more sharply curved and is covered by a transparent protective membrane called 'Cornea'. It is thin portion which is visible from outside.
2) Behind the cornea, there is place filled with a liquid called aqueous humour and behind this a crystalline lens which is responsible for image formation.
3) Between the aqueous humour and the lens, we have a muscular diaphragm called 'Iris', which has a small hole in it called pupil. Iris is the coloured part that we see in an eye.
4) Iris helps in controlling the amount of light entering the eye through 'Pupil'.
5) The ciliary muscles to which eye lens is attached helps the eye lens to change its focal length by changing the radii of curvature of the eye lens.
6) The light that eneters the eye forms an image on the retina.
7) The distance between the lens and retina is about 2.5 cm.