# Color of pure photon



## thinkFlashlights01 (Jan 20, 2015)

What is the _Color Temperature _of pure photon? I have always seen people talking about color temperature of light, put does pure photon have white color?


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## FRITZHID (Jan 20, 2015)

....That's a tough question.
From what I understand, light can act as both a wave and a particle.... depending on how viewed.
It's the wavelength that gives "light" it's color....
As far as the individual photons "color" per say, it may depend on the wavelength of origination or something along those lines. I'm not even sure we can detect the actual color of a photon with current detectors. I think it takes more than one for most color pixels in a ccd to even activate.
Have you done any research on photon specifics?


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## mattheww50 (Jan 20, 2015)

Color temperature of light corresponds to the spectrum of 'black' body heated to that temperature. i.e., is represents a wide range of photon energies (colors) whose census corresponds with what an ideal black body would radiate if heated to that temperature. So an individual photon of visible light can be ANY SINGLE color in the spectrum, depending upon its energy. Photons come in a wide range of energies, from far below visible light (which is around 1 electron volt) to literally billions of electron volts from some cosmic rays.Only a tiny portion of that range is detectable by our eyes as light.


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## Dr.Jones (Jan 22, 2015)

Actually even single photons have a frequency uncertainty and thus a range of wavelengths (corresponding to their energy uncertainty, and to their coherence length), thus a single photon can be white (and many are).


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## night.hoodie (Jan 22, 2015)

Dr.Jones said:


> Actually even single photons have a frequency uncertainty and thus a range of wavelengths (corresponding to their energy uncertainty, and to their coherence length), thus a single photon can be white (and many are).



To "see" something, don't you have to shine light on it? How would you do that? Isn't that the gotcha of the uncertainty principle, that as soon as you look at it, you change it? What was it before? How can you know?

---
I think I see (heh) what you're saying. But does it make any sense at all to say a single photon has a color when the color of that photon really can't be experienced first hand... similar to looking at something much smaller than a photon? We don't see it, we see what it left behind, so that's how we know what it was, or there's some other paradigm for vision and the light shined on it is not photons but something necessarily much smaller than photons.


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## StarHalo (Jan 22, 2015)

night.hoodie said:


> But does it make any sense at all to say a single photon has a color when the color of that photon really can't be experienced first hand...



You can experience a single photon, evidence suggests the totally dark-adjusted eye can register individual photons as singular points of light; if that photon happens to have the frequency that we experience as the color blue, you'll see a blue point of light.

The photon is a discreet packet of energy, not a physical mass like a billiard ball, so your act of "seeing" is actually just photons/energy being absorbed by your eye. Sort of like if you turn your light on and set it head down on a surface for a moment, then feel the now-warm surface where the light stood - photons/light energy absorbed by the surface and radiated as heat energy.


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## night.hoodie (Jan 22, 2015)

StarHalo said:


> so your act of "seeing" is actually just photons/energy being absorbed by your eye.



(Am I getting this?)-- "What color _is_ that photon you see?" -- nonsequitor! what photon?
--> "what color _was_ that photon you just saw?" -- oh, yeah, it _was_ blue.


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## StarHalo (Jan 22, 2015)

You _absorbed_ a discreet packet of energy that was resonating at the visible frequency of the color blue.


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## more_vampires (Jan 22, 2015)

Is there such a thing as a "pure photon?"

Example: So your playing with a spectrometer. You heat a copper wire until it emits light. You read the "stripes" of the color and identify the metal/metal alloy, it's not just one color... one kind of photon.

White is a color mix. Is one single, pure white photon even possible?


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## Ken_McE (Jan 22, 2015)

White is a psychological color, not a physical color. It is the sensation our brain generates when it gets a roughly even mix of the different colors within our visual range. A photon may be uncertain about its color, but when it is detected, it is forced to make a decision. If it picks a wavelength we can see, it will have a color, but I don't see how it could have all of them at the same time.

Thus, my vote is against the existence of white photons.


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## StarHalo (Jan 22, 2015)

No, there is no frequency for "white", a photon that is visible must be somewhere on the visible frequency spectrum. 

Each spectrum stripe in a spectrometer is generated by individual photons of similar frequency, whether visible or not.


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## night.hoodie (Jan 22, 2015)

Ken_McE said:


> A photon may be uncertain about its color, but when it is detected, it is forced to make a decision. If it picks a wavelength we can see, it will have a color, but I don't see how it could have all of them at the same time



superposition,,, hurts brains. I think at some point its required that one step back and forth from seeing accepted paradigm theory as actually, truely describing objective reality, and realize... well... its a lot like Camelot.

​


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## Dr.Jones (Jan 23, 2015)

The key word is superposition: The photon is in a superposition state of having multiple wavelengths, actually a whole range of them. A wavelength measurement (like detection with our eyes) lets that superposition collapse, the measurement changes the quantum properties, maybe giving blue as result. Or red. Or anything that was in the photon's range. 

Actually there can't be a single wavelength photon, energy-time uncertainty principle forbids it. Thr range may be small (like with lasers) but never zero width.


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