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This general Chemistry class is just starting off and we wanted to exercise our curiosity by asking questions. Can you please tell us why do we see all of the different colors we see? Someone told me that it is because of chromophores and I was wondering if that was true. Thank you very much.
Question Date: 2004-02-02
Answer 1:

I must begin by saying this question, although a good one, is rather more complex due to the physiology of 'the eye'. And yes, chromophores are involved. I will try to make it as explicit as possible so your students will understand.

Before I begin, a little physics to explain colors: The visible spectrum ranges in wavelength from 400nm to 700nm. So light of different wavelengths within this band are perceived to have different colors. If your class is interested in understanding what wavelengths are, I can explain that in another question. I just don't want to bog your interest down with too many details.

Photoreceptor cells in the retina of the eye contain photo pigments which absorb the light that passes through the cornea. There are four different photo pigments in the retina. Each photo pigment contains an opsin and a chromophore.

The opsin in an integral membrane protein that binds a chromophore molecule. Since each type of opsin binds to a chromophore in a different way and filters light differently, each of the four photo pigments absorbs light most effectively at a different part of the visible spectrum. Human retinas have three kinds of cones, containing red- green- and blue- sensitive photo pigments. Each of these pigments absorb and respond to light of different wavelengths. Our ability to see color depends upon the relative outputs of these three cones cells (photo pigments).

Hopefully this has answered your question. If you would like further information or detail about a specific area please let me know. I would be happy to explain it more.

Answer 2:

The chromosphere is an irregular layer of the sun above the photosphere where the temperature rises from 6000 C to about 20,000 C. At these higher temperatures hydrogen emits light that gives off a reddish color. This colorful emission can be seen in preeminence that project above the limb of the sun during total solar eclipses. This is what gives the chromosphere its name (color-sphere).

This is not related to why we see different colors! Every material has a different atomic make-up and different materials will absorb and reflect different wavelengths of light depending on their atomic structure. The world is illuminated by white light from the sun, which contains a wide spectrum of wavelengths including the visible spectrum from red to violet (the part of the spectrum which the eye is able to detect).

The color of a material is determined by the wavelengths it reflects the most from the white light. So for example a red piece of plastic reflects red color (~600nm) but mostly absorbs the other colors (350-590nm) so we see it as red. If a color is absorbed we don't get to see it. The color of an item is dependent on the range of wavelengths illuminating it. If you look at colors under an orange street lamp you will notice that things are illuminated only in different shades of orange. That is because the orange lamp has only one wavelength, so this is the only wavelength that can be reflected or absorbed.

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