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How do we see?

For discussing the functions of different structures of all organisms.

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How do we see?

Postby juan720 » Wed May 31, 2006 4:27 am

How do we see through the eye?
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Postby bpv » Wed May 31, 2006 5:03 pm

The light falling on every matter is either absorbed or reflected completely or partially depending upon the property of the body. We see an object when the light reflected from that body reaches our eye and forms an image on our retina.

The visible light consists of 7 colors. They are Violet, Indigo, Blue, Green, Yellow, Orange and Red (VIBGYOR). All the colors vary in their wave length. Out of this, the red has the highest wave length and the violet has the shortest.

All the other colors that we see are the combination of these or basically the primary colors. In fact Red, Blue and Green are the primary colors and all the colors of the above VIBGYOR are secondary colors.

The bodies reflect all or some amount of different colored light when it falls on their surfaces. A body appears to be white if it reflects all the light falling on its surface as white is the combination of all the seven colors of the color spectrum. Similarly it appears to be violet to red depending on the light it reflects. The object that completely absorbs all the light falling on it is called a dark body.



The light reflected from a body reaches the eye and enters through the transparent opening called the pupil. The region behind the pupil contains a fluid substance called the aqueous humor and through the aqueous humor the light passes and get converged or focused when it passes through the eye lens. The eye lens is capable of increasing or decreasing its thickness with reference to the distance of the object to be focused.

The region behind the eye lens is filled with a fluid called vitreous humor. As the rays get converged when it passes through the lens the rays focus at the inner layer of the eye ball called retina. The retina consists of numerous photoreceptor cells called rods and cones respectively. The rods are responsible for black and white vision and can function even at very dim light, while the cones are responsible for color vision and can function only at relatively bright light. This is the reason that you do not see colors in the dim light.

The image of the object is formed at the retina of the eye where rode and cone cells are present. The impulse is carried to the brain through the optic nerves and the brain interprets the sensation as an image.
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