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Optics question?

  1. Dec 31, 2003 #1
    I wasn't sure where to post this so if this is the wrong forum please excuse my ignorance.

    Here's my question:

    By shining ultraviolet light on a bottle and noting the color that it appears to be, can a scientist then confidently calculate what color that glass bottle will appear in white light? (knowledge of the type of glass that the bottle is made of is permissible)

    Also, just out of curiosity, would the type of glass actually make a difference? (i.e. Pyrex vs. flint, or cystal, etc.)

    Finally, is there a scientific "laboratory standard" for white light? If so, how is that standard defined? Ditto for ultraviolet light.

    Thanks in advance for any help that you can offer.
  2. jcsd
  3. Dec 31, 2003 #2


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    Last edited: Dec 31, 2003
  4. Dec 31, 2003 #3
    Re: Re: Optics question?

    Alright, I did have something in mind that I forgot to mention. I am particularly interested in colored glass bottles. Like a bottle that appears to be green glass in sunlight but maybe purple (Just guessing) in ultraviolet light. By looking at bottles only with ultraviolet light can science determine what color the bottle will appear to be in white light (or sunlight).

    Yes, I guess I can use Google to find the scientific standards, but I'm not sure how to use Google to answer the question about determining the "natural" color of stained glass from viewing solely with one particular wavelengths of light, say ultraviolet light.

    I'm actually interested in this question from a philosophical point of view. I do have some incandescent UV bulbs around here somewhere so I suppose I could check different colors of stained glass experimentally to see if different types of say green glass do appear to be different colors in the UV light.

    This whole question came out of a philosophical discussion concerning whether the color of a bottle is an absolutely objective property, or a more illusive relative subjective property.

    My main concern from a philosophical point of view is to figure out whether the scientific methods of optics can indeed be used to determine the "natural color" of a bottle (defined as the color as viewed in the "standard" of white sunlight) from information obtained by shining a specific frequency of light on it, in this case ultraviolet light.

    That whole scenario would be hard to do a Goggle search on.

    Believe it or not, this whole topic is actually a much smaller part of a larger conversation concerning the meaning of number and how it is associated with the quantitative properties of the universe. But I really don't want to get into that here. I am merely interested in the Optics question right now. Can scientists determine the natural color of stained glass in white light from having observed it using only a small part of the spectrum?

    At first I was thinking that the answer would be "yes", but now I'm starting to think that the limited spectrum of light could not be used to give the answer to what the glass might appear to look like if a wider spectrum of light was used. That certainly makes scientific sense, but has deeper philosophical implications.

    However, as you also mention, given the composition of the glass science might be able to determine the color that it would appear under any given wavelength without even performing any actual experiements. That also makes perfect sense to me and would once again make me simle!

    This is because within the scope of our discussion I am permitted to use any known science which includes the composition of the glass. My only limitation is that I am only permitted to shine untraviolet light onto the bottle (or no light at all if I don't need that data). My sole job is to determine what color the bottle will appear in white light using pure science and no white light.

    My only knowledge is the composition of the bottle, what it appears to look like in UV light, and all of known science that has already been previously recorded in history (including any previously performed experiments in optics, QM, or whatever).

    Armed with that information only can I be certain as a scientist to always be able to predict the color that the bottle will appear in white light?
  5. Jan 1, 2004 #4
    I don't think that you can.

    The color that you see is determined by the mixture of wavelengths. In the visible spectrum, there are wavelengths for shades of blue, shades of red, etc. When these wavelengths are present together, you can perceive the light as a blending of the different colors. White light is a mixture of roughly equal amounts of all the visible wavelengths present.

    The color of objects, except for luminescent ones, is determined by pigments. Pigments work by "absorbing" certain wavelengths. The wavelengths that aren't "absorbed" are "reflected". This "reflected" light determines how you perceive the object. (The reason that I use quotes is because I'm not quite sure of the actual physical processes that happen, but the human ideas of absorbtion and reflection are suitable explanations.)

    If a light source emits a purple light that is a mixture of red and blue wavelenths, and an object has pigments that absorb blue wavelengths, then only the red wavelengths will be reflected, and the object will appear red to you.

    So, shining an ultraviolet light will probably only tell you about how/if ultraviolet light is absorbed (or refracted, if you are investigating refraction). I think that you best bet would be, as Integral said, is to know the chemical composition.
  6. Jan 1, 2004 #5


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    What ever method of this sort you use, it can only tell you what it is now. Not what it WAS before aging. I think that must come from other means.
  7. Jan 2, 2004 #6


    First of all.....UV with appropriately short enough wavelengths are not visible to the human eye. Far UV...meaning UV that is somewhere in the neighborhood of 400 nm has a color associated with it simply because it is within the realm of the visible part of the EM spectrum.

    A person cannot see UV.....they see the fluorescence it causes in materials that it is incident on. As a cautionary NOTE here......I am not implying for one second that you go looking into a UV source. It WILL damage your eyes! So....just don't do it, and don't go looking at refelcted UV either...got it?

    The bottole onto which you shine a light source will reflect the wavelength of light that is characteristic of its atomic structure.

    If you shine pure red light onto a pure green bottle....you will see nothing. Why? Because the bottle's atomic make-up is such that it reflects light only of that one particular wavelength we call green. Shining any other wavelength of light on it will reflect nothing.

    Objects with color can be regarded as filters. They filter (reflect) light only of whatever wavelength(s) characteristic to their atomic structure, or make-up. Make sense?

    I don't know about the other materials you cited, but glass blocks UV pretty well. I can't give you percentages, because I don't recall right now what they are, but I don't think it's 100%. UV lamps are almost always made from quartz because quartz is transparent to UV...meaning quartz allows UV to pass thru it fairly unimpeded.

    I've asked the question about a 'white' standard also, and came to the conclusion that no....there really isn't a 'white' standard. To do relative color somparisons you can calibrate to your own white standard and measure relative to that. This kind of difference measuring isn't nailed to one set standard, but allows one to check for DIFFERENCES between two measured colors in color space.

    X-Rite has info about color work as does. You can begin by checking this site: http://semmix.pl/color/models/emo191.htm [Broken]

    It has alot of decent info about color, and standards. Also, you can do a search on Google and see what you come up with.

    Hope this helps.

    Last edited by a moderator: May 1, 2017
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