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Featured B How does light split into colors?

  1. Oct 27, 2018 #1
    Hi all

    Today I came home to find very discrete lines of colored light on my living room floor. Can anyone help me to explain this phenomena? I am familiar with dispersion but am wondering how the combination of glass and blinds is creating this effect.
    When I rotate the shutters as you can see from the pictures, the colors changed.

    Regards
     

    Attached Files:

    Last edited by a moderator: Nov 2, 2018
  2. jcsd
  3. Oct 27, 2018 #2
    that's very nice!

    Do you gave any glass ornaments on your sill?
    [quote fixed by mod]
     
    Last edited by a moderator: Oct 27, 2018
  4. Oct 27, 2018 #3
    My parter had something similar that was the result of hanging glass beads
     
  5. Oct 27, 2018 #4
    when the white sun light enters through a glass leaf at a specific angle, the light decomposing to the original color according to it wave length, the red color has a longer wave is angled at a lower angle, the yellow at a larger angle , then the green color , then the blue . so the the white sun light decomposes into spectrum colors like the rainbow.
     
  6. Oct 28, 2018 #5

    LURCH

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    Just a visual impression; this spectrum appears to be too spread out to be coming from the glass in your window. Is there any glass or reflective objects out in the yard? Or as has been suggested above, maybe a glass ornament, but rather than on the sill, perhaps hanging from the eve, or a branch a few feet away?
     
  7. Oct 28, 2018 #6

    Tom.G

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    If you look out that window you will see a transparent object. That object is wedge shaped and its distance from the door is about 2.8 times the short dimension of the floor tiles. If the photo was taken about 1.5 hours before sunset, the object is probably about 1.8 floor-tiles above the floor, also assuming that there is no obstruction between the object and the window.

    Notes: since there were no dimensions given, the floor tiles were used as the 'master yardstick'. using rather simple geometry, the optical distortion of the floor tiles to find the angle between the color rays. knowing the ray angles and the dimensions in units of 'floor tiles', the point of convergence was found to be 4.04 tiles from the start of the rays. subtracting the distance to the door gave the distance to the point of convergence. the height of the prism-like item was estimated from the assumed solar elevation of 22.5° at 1.5 hours before sunset and the distance to the start of the rays.

    Cheers,
    Tom
     
  8. Oct 28, 2018 #7
    I am now very curious to see what is outside his window!
     
  9. Oct 29, 2018 #8
    Thank you for the replies everyone!

    Some more details and pictures:
    • No glass beads. However there is "light dome" which is above our bycicle shed. If you look in a straight line from where the lines originated you do not see the dome. It is slightly to the left (see second picture and sketch).
    • The blinds are plane white blinds with a fine vertical structure going over the entire height of the blind (barely feel the structure when touching).
    • The picture was taken at 12:38, 27th of October (before winter time, 28th of October time was adjusted).
    • I live in Neerpelt area, Belgium.
    • I included a sketch of the situation with some reference measurement (tile).

    If any other info is needed feel free to ask.
    Even if it is the dome causing this, I would still love to know how to lines became this discrete/high intensity.

    Regards
     

    Attached Files:

  10. Oct 29, 2018 #9
    The lines are most probably caused by the vertical blinds. It would have been a good idea to remove them and see if you get a continuous spectra.
    The intensity is relative The light from the external source (whaterver it is) was just brighter than everything else. It wouldn't appear that bright compared to direct sunlight.
     
  11. Oct 29, 2018 #10
    I don't have anything to add to the discussion, but those pictures in the OP are very cool! I have never seen anything quite like that. Thanks for sharing them!
     
  12. Oct 29, 2018 #11

    LURCH

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    I think the dome shape of the skylight cover explains how the light came in during the middle of the day. Apparently, even though the sunlight was coming nearly straight down, somewhere along that curve was a spot with just the right angle to send the light into your window. Was it raining just before you saw this?

    A very cool effect. Thanks for the pics!
     
  13. Oct 30, 2018 #12
    What I don't understand is this: if a light source (Sun or whatever it is) is refracted from matter, it comes out at an angle different from zero, even if the incoming beams were parallel. Then, how can the colured beams in the OP's photo be so parallel and not diverge at all?

    --
    lightarrow
     
  14. Oct 30, 2018 #13

    phinds

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    Odd, I see them a CLEARLY not parallel.
     
  15. Oct 30, 2018 #14

    LURCH

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    As Tom mentioned in Post #6, th lines are not exactly parallel. That is how he calculated a point of origin.
     
  16. Oct 30, 2018 #15
    I mean, *every* single beam doesn't seem to diverge appreciably, it seems a laser beam.

    --
    lightarrow
     
  17. Oct 30, 2018 #16

    OmCheeto

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    Do not ever let me know where you live, as I will find you, and I will kill you.........

    follow.the.lines.png


    My answer is: The source is somewhere between what you said, and infinity.

    I think it was the spacing of the colors that didn't seem right to me, based on my observations.
     
  18. Oct 31, 2018 #17

    Tom.G

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    That's mostly because of the wide-angle camera lens.
    If you assume that the floor tiles are rectangles, from the OPs photo you can measure the spacing between the Red and Green light beams as a percentage of the tile size (tile width in the photos). Do this for the near edge and the far edge of a tile. This essentially gives you the divergence (relative horizontal 'slope') of the light beams across the tile.

    The spacing of the individual lines of color was because the continuous spectrum was blocked by the vertical window blinds. The angle of the blinds was such that there was visually enough space between them to let slivers of light thru. Or to put it another way, the space between the blinds acted as slits for the spectrum to get thru and shine on the floor. The individual beams did not disperse much because the source of light, the 'light dome', was much further away than the slits in the blinds. (Besides any beam divergence is difficult to spot because of the wide-angle camera lens.)

    Aww, I'd rather be friends (or frenemys if you insist :biggrin:)

    Cheers,
    Tom
     
  19. Oct 31, 2018 #18

    phinds

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    What is it that makes you think it was a "wide angle" camera lens? Seems like very normal pics to me.
     
  20. Oct 31, 2018 #19

    Quite a few comments since I last looked.


    Consensus is :


    Light Source (sun), prism like object, dispersion, then the blinds prevent all the colours coming through hence the dark bands?


    The blinds also have a mirror effect “straightening” out the angles as it were projecting the remaining colours on to the floor? Is that possible?


    Those rays do look straight and the blinds seem uniform angle wise.


    I also would like to see what the dispersion object is, you can get this with objects other than a prism apparently but not as pronounced (quick google)
     
  21. Oct 31, 2018 #20

    OmCheeto

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    I was just amazed at how quickly you solved that.
    It took me a week to solve a similar* problem, back in April.

    ----------
    *Similar, as in, basic geometry, that is.
    Dreading spending another week working through this one.......

    ps. Fun problem! Thanks, @YeeHaa !
     
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