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The temperature of light?

  1. May 22, 2015 #1
    Hi, I'm learning photography and I learned that the color temperature of Candle light is about 1850K. However if the temperature of a candle light was 1850K I think it would burn you up, so my question is. What is the difference between Color temperature and temperature of an object? why does the candle light give off a color temperature of 1850K if it's not its real temperature?

    I know this: The color temperature is the color a black body would give off at a specific temperature, but how come other objects than black bodies (candle light, floureescent light etc.) can give off those colors at much lower light?
    Last edited: May 22, 2015
  2. jcsd
  3. May 22, 2015 #2
    Non-black body radiation is dominated by specific emission lines. The yellow color of candle light is mainly caused by carbon. The resulting impression of the flame color corresponds to the emission of a black body with a higher temperature.
  4. May 22, 2015 #3
    Does that mean that the color we see from non black-body objects is not a color that originates from that objects temperature but rather from the photons of light that the electrons give off when non-black bodie's atoms interact in chemical reactions?

    How do these photons differ from the photons given off by a black body if the color is the same? Are they the same photons with the same amount of energy?
  5. May 22, 2015 #4
    Wait i have an idea: If you have red color from a candle and red color from a black body, both photons have the same energy level. The photon from the candle got it's energy from the exotermic reaction, while the black body photon got it's energy by heating the atoms up. In both cases the electrons jumped between quantum levels such that the difference in energy emitted is the same?
  6. May 22, 2015 #5


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    I doubt that the spectrum from a candle flame is very different from black body. After all, what you are seeing is the light radiated from lots of little black bodies (the carbon particles).
    But when you are talking about "colour" you are referring to the subjective effect of the spectrum of the light reaching a human eye. The tristimulus theory of colour vision tells us that you can give a very good match for any particular colour with a suitably weighted sum of any three or more Primaries. This is the basis of Colour TV.

    But, back to the OP. Watching the spectrum of the light emitted from a candle does not involve getting close enough to burn yourself. The actual energy per unit area of your body is minuscule and that is what counts when considering how 'hot' it will feel. They are two totally different concepts - consider the Sun.
  7. May 22, 2015 #6

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    You are confusing temperature with heat. You can stick your hand in a hot oven without burning it, but boiling water (at a lower temperature) will cause severe burns. That's because the air in the oven has a high temperature, but doesn't carry much heat. It's the same with light.
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