45. How do eyes work?
We see with our eyes. Our eyes are lodged into the bony sockets in
the skull. The muscles in the socket turn them so that we can see in
any direction. Each eye is a fluid-filled sphere with a transparent
window at the front, known as the cornea. Pupil is a small hole in the
centre and behind it, is the coloured iris.
A convex lens is present behind the iris. In the rear part of the eye is
a screen called retina. Millions of receptor cells called rods and cones
make up the retina. Rods are sensitive to dim light and are used for
black and white vision. Cones respond to bright light and can detect
colour. Retina is connected to the brain by the optic nerve.
The lens and retina have a fluid in between known as aqueous
humor.
Light rays from an object fall on the cornea of our eyes and when
these rays pass through it, they are bent so that they pass through the
pupil and into the lens. The light rays are bent again as they pass
through the lens and they are focused into the retina to form an
inverted picture. The picture reaches the brain through the optical
nerve. The brain again inverts the picture and we see the object. This
whole process is very fast. Too much light can damage the retina, so
in bright light, the pupils get small.
