why light is consist of seven or more color not only three color?

Discussion in 'Physics & Math' started by Paul Leung, Feb 22, 2014.

  1. Paul Leung Registered Member

    Messages:
    16
    I found another photo, and this photo is more clear to show there are three color light overlap together after light through a prism.
    In this photo, red color light, green color light and blue color light is nearly fully separated by the prism.

    View attachment 6944

    In this photo, it is clear to see there are three circle like shape overlap together.

    if light consist of seven or more color light, it will be at least seven circle like shape with nearly equal size overlap together,
    but in this photo, it is clear only three circle like shape overlap together.

    and below is the source
    gadgetscience.com/explanation-of-color-from-a-prism/
     
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  3. Neddy Bate Valued Senior Member

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    2,548
    I hope the light source in those photos is not an RGB display screen set to display "white".
     
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  5. el es Registered Senior Member

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    322
    Newton had good reason to have yellow as a "pure" color of the visible spectrum. He used one prism to get the spectrum, then he used a screen to block the other colors, but let yellow through a slit. This yellow was passed through a second prism and yellow came out. Yellow wasn't a composite color.

    According to Paul Leung, the yellow through the second prism would separate into red and green because it is a composite of red and green.
     
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  7. Neddy Bate Valued Senior Member

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    2,548
    That's a good point, thanks.
     
  8. billvon Valued Senior Member

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    21,635
    Yes - but that' s not the same yellow you see coming through a prism.

    Green and red combined are SEEN as yellow by human eyes because of how our eyes process visual information. In other words, we see a pure yellow light at 580nm the same way we would see pure green (540nm) and red (680nm) lights mixed together because they cause the same firing rates in the cones (color sensitive cells) in our eyes - not because their wavelengths are the same.

    And not everyone is the same, either; someone who was colorblind might claim that red and green combine to make blue, and he'd be just as right as you are. Likewise, someone with a better imaging system in their eyes - who can see the color range that, for example, the Martian rover can - would claim something completely different. They'd see green and red and think you were crazy for claiming it was yellow. The only reason most people agree that red and green make yellow is because most people have the same eyes, with the same fundamental limitations.

    (And here's something that will really bake your noodle. Most people think the change from red to violet to blue is continuous; red and violet are actually the two farthest apart colors there are in the spectrum!)
     
  9. Paul Leung Registered Member

    Messages:
    16
    I found someone did a pure yellow experiment with two prism but has different result to newton.
    quote:
    //////////
    Much later, in the 1720s (after Newton's 1704 Opticks), Giovanni Rizzetti, in Venice, specificed his own conditions for what constituted a good experiment with two prisms:

    care is to be taken that the second prism is not too distant from the first, nor the slit, through which the light of one colour is transmitted from refraction at the first prism to the second, is too narrow.
    These, of course, were exactly the opposite of Newton's criteria. And the conclusions that Rizzetti reached were likewise quite different.
    For him, pure yellow light transformed itself, upon a second refraction, into red, green and indigo--with the yellow itself disappearing.
    //////////

    and the source
    www1 .umn. edu/ships/updates/newton1.htm

    more details from page 96 to 99
    books. google. com. hk/books?id=Bk4sUpSx1LsC&pg=PA96&lpg=PA96&dq=
    Giovanni+Rizzetti+prism&source=bl&ots=Qpqr9CrWoV&sig=IjueOTrIsqTjdK_DmzHT_7Y69mE&hl=
    zh-TW&sa=X&ei=QPsdU_2aKOeYiAeM24CQCg&ved=0CDcQ6AEwAw#v=onepage&q=Giovanni%20Rizzetti%20
    prism&f=false
     
  10. rpenner Fully Wired Valued Senior Member

    Messages:
    4,833
    But Giovanni Rizzetti was working with confirmation bias, didn't win the argument, wasn't working with pure spectral monochromatic light. There is just one physical reality and thus, ultimately, there can be only one science as humans test their ideas against reality and discard those ideas which don't match reality with precision. Having gotten on the right track, as with Newton's separation of white light into spectral colors, future scientists tend to refine both largely correct observations and largely correct theories.
    The physical significance of Newton's correct notion would become evident in the physical important of Fraunhofer lines and the study of human perception of color that led to color-matching technology in paint stores.
    http://en.wikipedia.org/wiki/Fraunhofer_lines
    http://en.wikipedia.org/wiki/Emission_spectrum
    http://en.wikipedia.org/wiki/Hydrogen_spectral_series
    http://en.wikipedia.org/wiki/CIE_1931_color_space
    http://en.wikipedia.org/wiki/Planckian_locus
     
  11. kyle0 Registered Member

    Messages:
    1
    Nice Share... i am interesting in this thread.. it's great.
     
  12. el es Registered Senior Member

    Messages:
    322
    The outcome of such an experiment depends on how it is done. Since our sun appears as a disc, not a point source, the first prism yields 2 spectra not one.

    Close to the prism you can see the extreme red and yellow of one spectrum and the extreme violet and blue of the other spectrum. Both of these spectra disperse over distance. Newton picked a location where the two spectra coincided for a monochromatic yellow. Closer to the prism you can sort out a perceived yellow that is polychromatic and get the results that Rizzetti got.
     
  13. Paul Leung Registered Member

    Messages:
    16
    The article of "Explanation of Color From a Prism" has stated although people can perceive around 10 million colors,
    prism colors are classified as one of the following seven,
    and then it stated if you have a dark room and a bright sun, it will show up beautifully at a distant wall.
    There is no reason to use a RGB display screen set to display "white" as light source to
    get a wrong result of spectrum on wall.

    And there are more photos I found and it is using sunlight as source.

    blondearieschick.blogspot.hk/2011/04/59365-sunshine-and-gratitude-again.html
    eddybluelights.blogspot.hk/2011/12/when-is-window-prism.html
    mamameglutenfree.blogspot.hk/2012/02/rainbow-rainbow-on-wall.html
    wwwmountain-momentscom.blogspot.hk/2013/12/rainbows-on-wall.html#.UyQF5PmSw-J
    imageryoflight.wordpress.com/2012/08/29/spectral-colours/
    lovemyscience.com/crystalprismspectrum.html
    thehousewherethecricketssing.blogspot.hk/2012/02/colour-of-light.html
    art-by-michael-perchard.blogspot.hk/2013/03/magnificent-ocean-my-studio-awesome.html
    capnbob.us/blog/2005/11/19/damsel-sends-you-rainbows/
    knittingonthecam.blogspot.hk/2006/11/eye-candy-rainbow.html
    zaporacle.com/in-memoriam-nathan-zap-1919-2012
    ladolcevitaleann.blogspot.hk/2008/05/glad-game.html
    beverlyfaye.hubpages.com/hub/Rainbows-Symbols-of-Promise
    penelopepuddle.blogspot.hk/2012/05/runaway-rainbows-in-my-room_15.html


    And a rainbow maker youtube video
    youtube.com/watch?v=N5rsQwLq0EY
    View attachment 6961
     
  14. Paul Leung Registered Member

    Messages:
    16
    Giovanni Rizzetti didn't win the argument was not because of wasn't working with pure spectral monochromatic light or confirmation bias.
    It is because the prism he used is made at Venice and not made at England.

    In "The Uses of Experiment: Studies in the Natural Sciences"

    books.google.com.tw/books?id=AWrgygRWERsC&pg=PA99&lpg=PA99&dq=
    Rizzetti+unchangeble+color&source=bl&ots=HTaPPThOSO&sig=ntc3C15PkyreyZVRuwPsi1g07Wg&hl=
    zh-TW&sa=X&ei=M78hU7PNKoeViQfvtoGADg&ved=0CC8Q6AEwAQ#v=onepage&q=Rizzetti%20unchangeble%20color&f=false

    Page 98
    /////
    The English claimed that Rizzetti, having made use of Prisms made at Venice,
    which are not of so pure a Cristall as ours, has been led into the many mistakes
    he has asserted for convincing proofs. Rizzetti's bad instruments have rendered him
    ridiculous for ever.
    /////

    Page 99
    /////
    Algarotti reported that when he had tried the experimentum crucis he had failed to
    produce unchangeabe colours, because 'our Prisms in Italy are of no other use than
    to amuse Children or hang up as a fine shew in some window in the country'.
    In contrast,'the crucial' experiment worked well with prisms sent from England;
    these we esteemed as sacred.'
    /////

    Page 100
    /////
    'It would be a pretty situation', the Italian exclaimed, 'that in places
    where experiment is in favour of the law, the prisms for doing it work well,
    yet in places where it is not in favour, the prisms for doing it work badly'.
    For such critics, Newton's prisms never became 'transparent' devices of
    experimental philosophy.

    /////

    I doubt light is consist of seven or more color light is because the result of
    a beam of white light through a prism is weird.

    why a beam of white light through a prism, but output a little bit of red light?
    below using a light through a prism image credit by Adam Hart-Davis as example.
    View attachment 6962
    View attachment 6963
     
  15. rpenner Fully Wired Valued Senior Member

    Messages:
    4,833
    This follows because the perception of two colors as "not the same" is finely grained and is a large part of why color vision is a useful adaptation for animals even if they lack the ability to name colors.
    That is just one person's opinion on what the names of the colors should be. Classification systems exist to name things and even if the phenomena is continuous a classification system will treat it as discrete. But human perception works on the phenomena (which may be continuous) not the naming.
    Because the sun has small angular measure from the surface of the Earth, a prism of only modest dispersion can cause the refraction differences between red and blue monochromatic light to separate more than the angular measure of the sun.
    That does not follow from your sources. In fact there is not one recipe for glass, but many. Different glasses may be equally transparent but have different optical properties such as refractive index and dispersion. Thus why the identity and manufacturing process for the prism must certainly matter, the physical point of origin has never been shown to matter. Indeed, cheap, flawless prisms are available today made in neither England or Venice and they all support Newton's theory of light and color. Unless you actually have access to Rizzetti's instruments, you can't tell me the composition of the glass they were made from or their overall optical quality.


    Scientists agree, partly because the dispersion of light through a glass prism is not simple (as dispersion is not a linearly related to wavelength or frequency). That's why for scientific study of the spectrum, man-made diffraction gratings are the state-of-the-art.

    Yes this 1997 picture by Adam Hart-Davis is described as being "A little like Newton's famous experiment, with white light split up into a full visible spectrum."

    http://gallery.hd.org/_virtual/ByCategory/natural-science/prism/

    But it is not clear that this is an accurate photograph of the spectrum of a blackbody spectrum when it might have been just as easy to do multiple exposures of monochromatic laser illumination and use darkroom manipulation to adjust the white balance afterwards (or to use a lightbox that used a white mixed from three monochromatic sources). Likewise, it may have been extensively digitally manipulated for contrast and aesthetics. Thirdly, color film color reproduction need not match human perception exactly, but because of the banding effects seen in this photograph, I think that's an unlikely explanation.
     
  16. el es Registered Senior Member

    Messages:
    322
  17. Paul Leung Registered Member

    Messages:
    16
    All of the photo of a beam of white light through a prism I found on the internet like Adam Hart-Davis's photograph,
    should you provide an accurate photograph of the spectrum of a blackbody spectrum.
     
  18. Paul Leung Registered Member

    Messages:
    16
    There are some spectrum of low pressure sodium I found.
    And the spectrum of low pressure sodium consist of red light and green light.

    palomarskies.blogspot.hk/2009/05/why-astronomers-love-low-pressure.html
    starlab.uk.com/Spectrometer/Spectrometer.htm
    neon-lighting.com/articles/Types%20of%20Lamps.htm
    www . physics.csbsju.edu/astro/spectra/RealSpectra.html
    commons.wikimedia.org/wiki/File:Low-pressure_sodium_lamp_700-350nm_widened.jpg
    home.freeuk.com/m.gavin/grism2.htm
    www . nezumi.demon.co.uk/nonad/spectra.htm

    Should you explain why the spectrum of sunlight on wall seem like three circle like sharp overlap together,
    And in some situation, yellow and cyan light was nearly fully vanished on the spectrum of sunlight on wall.

    gadgetscience.com/explanation-of-color-from-a-prism/
    View attachment 6979
     
  19. el es Registered Senior Member

    Messages:
    322
  20. rpenner Fully Wired Valued Senior Member

    Messages:
    4,833
    This photograph is not evidence -- color photography does not guarantee the same sensations as actually experiencing an event. In addition, Adam Hart-Davis could have easily used a professional light source with a non-continuous spectrum (or just have used a cheap fluorescent source). A well-defined spectrum is actually exactly the hardest object in color photography to accurately depict, for if color photography could accurately portray the relative colors and intensities of all monochromatic light then normal objects illuminated by normal light sources would pose no problem at all.

    Your very first link refutes your claim. Astronomers love the yellow illumination of low pressure sodium lamps because it is spectrally pure and thus technically easy to remove from instrument data. Typically when arguing for a proposition one is careful not only to cite material supporting one's point but to carefully quote a small part of it where it directly supports your claim.

    The first photo is likely synthetic -- a fake meant to be representative. The second is a pair of stills extracted from a video -- the image processing of streaming video is even more problematic than simple color photography.

    In short, your position is unscientific, your sources don't support contradict your claims and you have relied on bad data (fakes, unreliable color reproductions, and digitally manipulated images).

    The issue is immediately resolved by experiment.

    For less than $300 you can buy an 18-watt low pressure sodium lamp fixture and bulb and optical quality prism and prove to yourself both that there is no significant color distinction between red and green painted objects when illuminated only by such light and no significant dispersion of colors by a prism.
    Or, depending on where you live, for less than $5 you can go to a parking lot illuminated by low pressure sodium light and use the dispersion of an old CD (being substituted for a diffraction grating) to show that it is spectrally pure.

    But you don't need to do such an experiment because it's done every day. Even people who want to sell low-pressure sodium bulbs point out that they are monochromatic:
    https://www.sylvania.com/en-us/products/high-intensity-discharge/Pages/low-pressure-sodium.aspx

    Actually the truth is a bit more complicated, because low pressure sodium lamps are often given a little gas or mercury to cause them to reach steady illumination in a low time, and color photography can obscure the relative strengths of the sodium yellow from contaminants. However, the electric pickle also emits this sodium yellow light but because of the significant shock hazard I cannot recommend that you use this light source:
    http://hyperphysics.phy-astr.gsu.edu/hbase/quantum/sodium.html
    http://www1.assumption.edu/users/bniece/spectra/lightsources.html
     
  21. el es Registered Senior Member

    Messages:
    322
    Using a yellow highlite marker, draw a line on a white piece of paper. Look at it through a prism, it doesn't separate into red and green.
     
  22. el es Registered Senior Member

    Messages:
    322
    I brought up the helium spectrum on the computer monitor and got out one of my prisms. Turning the prism on end and rotating it while looking at the "yellow" line, it went from almost a perceived full spectrum to two thin lines of red and green with a very faint blue line.
     
  23. el es Registered Senior Member

    Messages:
    322
    The photoelectric effect doesn't concern itself with perceived colors, only the energy of the photons. The effect would prove that a pure spectral yellow exists and that there is a difference between Newton's yellow and Rizzetti's yellow.
     

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