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COLOR VISION |
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HUMAN VISION AND COLOR
Color is a part of the human vision system. Without color vision, color would be merely a variation of light waves. The ability of the human eye to separate the various frequencies of light waves allows us to distinguish different colors.
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The blue and green light waves from the sunlight are absorbed by the apple's skin. |
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| Red light is reflected | |
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The apple appears red |
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We see the apple as red because the image of the apple's red skin affects the red sensitive vision cells of the eye more than it affects the blue and green vision cells. We then identify the apple's color as being "red".
Vision cells are positioned on the retina, located on the back inside surface of each eye. The cells that allow us to see color are called "cones". There are several types of cone cells distributed across the retina. There are cones that are especially sensitive to red. Others cone cells are especially sensitive to green or blue.
The colors red, green and blue are also the primary colors of light. That means that all other colors can be recognized by the eye as mixtures of different intensities of red green and blue.
THE COLOR SPECTRUM
A glass prism can be used to separate white light into its various wavelengths or frequencies of light. This shows that white is actually a mixture of color.
| White Light | ||
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| Prism |
Different colors of light have different wavelengths.
| The wavelength of color light is measured in nanometers. | ||
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red orange yellow |
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| The numbers shown here are the number of nanometers between each wave of light. | ||
| green | ||
| blue | ||
| violet | ||
How small is the distance between each wave of light? Well there are one billion nanometers in one meter. So the waves of light are extremely small, but they make all the difference in the colors that we see.
It is this difference in wavelengths of light that the human eye detects as different colors.
Note: Colors such as magenta and brown are not in the spectrum produced by a prism. However, magenta illumination can be produced by mixing red light and blue light. Brown light is actually a low intensity yellow light or a low intensity of orange light depending on the type of brown.
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| Red and blue light make magenta | Yellow and orange dim to brown |
Much of what we see as color is a combination of human vision and the science of light.
| All images are original graphics or photography
by Robert Truscio © 1997- 2009 (All rights reserved) |
