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Colors in white light visible to the naked eye?

  1. Aug 11, 2010 #1

    Simple question: Should they be visible to the naked eye?

    I googled it, but haven`t found any closely related material :)
    I`m really interested in this, but have no required knowledge to really answer this question nor explain it properly.

    Best Regards
  2. jcsd
  3. Aug 11, 2010 #2
    You couldn't see anything if colors were not visible in 'white' light. I'm taking slight liberties with your question because there is no such thing as 'white' light. You see color because the object you're looking at absorbs the other wavelengths of light that your light source(s) illuminate it by.

    If this isn't quite what you meant, try rephrasing the question and we'll have another go at it.
  4. Aug 11, 2010 #3
    When an object is white, it means that it is reflecting radiation across the spectrum of visible light. White looks so because it is so reflective. If only red light hit the white object, it would look red, if only green light, then green. For some reason, when combined, reflected radiation from the sun, across the visible spectrum is translated by our eyes and brains into what we perceive as white.
  5. Aug 12, 2010 #4

    Ok. You have given me a reasonable answer for my question (which wasn`t precise, as i assumed).
    A better version of the question would be: Can we also perceive the colors of all the wavelengths that are contained in the light which we see as white with our bare eyes? :)

    Best Regards
    Last edited: Aug 12, 2010
  6. Aug 12, 2010 #5


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    Staff: Mentor

    Yes. The question is essentially redundant: what we call white is the mixture of all the colors we see.
  7. Aug 12, 2010 #6
    White light may also contain other wavelengths, but we don't see this. We only see the visible part (of course). Nothing prevents wavelengths outside the visible range to be included in the mix. Whether some is included or not, we see the same white. To see the colours of white light, get a glass triangular prism.
  8. Aug 12, 2010 #7
    It all comes down to this: Do I really need a glass triangular prism? Can a "...bare eye..." see them?
  9. Aug 12, 2010 #8
    The eye collects the information, so yes we see them. To make it easy on us, our brain translates the information into what we perceive as white. I think.

    You have to realize, that colors, as we perceive them, are nothing more than a mental construct. Some people have anomalous brains, which mix up our senses, and they see colors when they hear sounds, smells, etc.

    Maybe someone can chime in and explain how and why we perceive a mix of light of different frequencies as white.

    When we use technology in spectrometry, to collect information about a light source, what we collect is raw data identifying the frequencies individually including frequencies that our eyes are incapable of seeing. If we want to make an image out of it, we have to assign colors to frequencies and produce an image we can see. The point is that the color we see, is not as important as what it stands for. Our do the same thing, they assign certain frequencies to colors codes which our brain uses to make sense of what we see. For practical purposes, picking out many frequencies out of a mixture of different frequencies doesn't help us much. There would be no real purpose for that.

    On the other hand, you never know what the subconscious knows. Our bodies communicate with itself independent of conscious thought. When light hits us, a signal is sent to the Pineal gland telling us it is day, when we are in the dark, our pineal gland releases melatonin, a hormone which is linked to sleep cycles. Blue light specifically is responsible for halting melatonin production, before bed, if your where goggles which block blue light, your pineal gland can produce melatonin.

    Last edited: Aug 12, 2010
  10. Aug 12, 2010 #9
    You are referring to synesthesia, a condition which I happen to have, but that`s not the reason why I asked the question above btw.
    Yes, that would be interesting. I was assuming that the topic would require some physics and maybe biology knowledge?

    Anyway, the whole point of the topic was to check if it`s known for one to, while looking at a lamp post light let`s say, see the white AND the all the wavelength colors that are contained in it (in the visible spectrum range of course) at the same time, because I can actually see it as described.

    P.S. This is why the thread was in the Scepticism & Debunking forum before it was moved.
  11. Aug 12, 2010 #10
    Thank you for the info. I will look into it more closely.
  12. Aug 13, 2010 #11
    The eye has three types of light sensitive cells called cone receptors. Each is sensitive to a different range of wavelengths. Mixtures of light we see as strongly colored stimulate one or two of these more strongly than the others. Light that stimulates all three is seen as white. (an oversimplified explanation, the eye also has rod receptors that aren't strongly color sensitive, and the response of the cones is more complicated, but this suffices)

    Your eyes respond to all wavelengths in the visible range, your brain interprets the resulting signals as various colors. It's really not at all clear what you're asking...if this qualifies as "seeing colors in white light", then the answer to your question is "yes": you do see them, you see them as white. If you're seeing white light as having color, then it may be a symptom of a serious problem, and you should probably consult a doctor ASAP.
  13. Aug 13, 2010 #12
    No, because the point sources for each color are adjacent to each other at a molecular level, but our brain imagery doesn't have this spacial resolution. Use filters to see the colors one at a time.

    In other words, if you could separate the colors of white light coming off a blank screen with your eyes, what would define the location of each color? Why should red be "there" and blue be "here"?

    Think of pixels on an LCD computer screen, it all comes down to resolution.
  14. Aug 13, 2010 #13
    Yes. This is what i was typing about in the previous posts.

    Look at a strong light source that radiates white light (like on a lamp post) from medium distance. Try placing something in front of your eye while looking at the light source to block your sight and then lower it gradually and very slowly while watching the 'edges' of the light. Maybe you`ll understand what I was referring to all this time.
    Last edited: Aug 13, 2010
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