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Mystic_Cannibal
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Registered: 12/09/05
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Last seen: 11 years, 6 months
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What determines an molecules color?
#7881292 - 01/15/08 12:17 AM (16 years, 18 days ago) |
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Hey I was just wondering if anyone could explain how certain things have different colors, I understand all about rods and cones and the brain etc. I also understand that light waves of certain colors on the spectrum are absorbed instead of being reflected to the eye but what determines which colors are absorbed and which are reflected back? Why is the air clear? Does mixing elements that are the same color alone ever produce a different color when they join together? Is somethings color determined only by the mix of original colors from the atoms inside it?
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im_on_a_boat
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Registered: 04/06/06
Posts: 3,950
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if you 'understand all about rods and cones [in the eye] and the brain', then why are you asking this question?
the air is not clear.. it just doesn't have enough density in its molecules to be able to reflect light back to your eye/brain.
the answer to the elements question is yes.. if i am understanding you correctly.. it should be a pretty obvious yes too. 
an objects color is determined by your eye's interpretation of the signals that it is sent from that objects molecules. your eye determines the color, not the 'mix of original colors from the atoms inside it'.
at least this is how i feel and have been educated to know.
of course it's 2 am and i'm running on very little sleep so i might read this tomorrow and be like what the fuck was i talking about. but i hope that maybe helped.. at least enough for tonight.
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karma35
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Registered: 09/07/07
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Last seen: 5 months, 9 days
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There isn't a simple answer to your question, as several factors determine the color of objects. The wikipedia page is a good place to start:
http://en.wikipedia.org/wiki/Color
See the section titled "Color of Objects" in particular.
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Toboggan
I Am My OwnSavior


Registered: 06/25/03
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Last seen: 11 years, 10 months
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Re: What determines an molecules color? [Re: karma35]
#7885519 - 01/15/08 08:00 PM (16 years, 17 days ago) |
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I can't answer all your questions but yes the structural properties of molecules influence which wavelengths of light are absorbed/reflected.
For organic molecules conjugation (alternating pi bonds) and presence of functional groups affect the color. Most organic molecules for example are white but highly conjugated ones can show intense color (like beta-carotene and indigo).
Electronegative functional groups can contribute to color too. If we take indigo which is blue and compare it to 6,6'-dibromoindigo we see that adding 2 bromine atoms to the molecule makes it purple (6,6'-dibromoindigo is Tyrian Purple which is an ancient dye that was extremely expensive, hence, royal purple).
Inorganic molecules and organometallics work a little differently but in all cases its about the electron configuration of the molecules. Its these electron configurations which determine what wavelengths of light will be absorbed.
Its a pretty complicated question with a complicated answer. A brief explanation of the physics of it is here http://en.wikipedia.org/wiki/Chromophore. You can find more detailed info if you look around. Try a book on UV/Vis spectroscopy at your library.
-------------------- "A man who wants to lead the orchestra must turn his back on the crowd"
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