The human eye

The Human eye is a very intricate device. But, the eye is useless without light. Nothing can be seen in pitch darkness. The work of the eye begins only when there is light. How does the eye work?

The light from the object being seen falls on a special surface inside the eye called the retina. The retina converts light to electricity. These tiny bits of electricity (signals) are carried to the brain by the optic nerve. The brain analyses these signals and identifies the object. The information gathered about the object includes its colour; texture (to some extent); depth (three dimensional aspect); distance from us and motion.
The light that falls on the retina must be sharp and not hazy. It should be focused. The eye lens achieves this. The eye lens is a transparent bag filled with a transparent fluid. It is oval in shape and can flatten or bulge. This makes it possible to see near objects just as clearly as distant objects.

The amount of light that falls on the retina is very important. Very strong light can damage it. A mechanism to control the amount of light is necessary. The iris provides this mechanism. The iris is the coloured disk of the eye, which has an opening at the centre known as the pupil. The pupil is narrow in bright light, thereby allowing only a little light to enter in and wide in dim light to allow more light to enter in.
The eye needs to keep moving to look at different objects. Strong eye muscles help in this. Besides, to see clearly, the eye must be clean. The eye is kept moist by tears so that any dirt can be swept to the corner of the eye. Every blink helps in this cleaning process.