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Thread: Colors question

  1. #1 Colors question 
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    Why is it that the underside of a CD shows a rainbow? My intuition says that it'd just show the surroundings, or whatever it reflects, but that's obviously wrong. So why does a CD's underside show the rainbow?
    My guess would have something to do with the scratches on it.


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  3. #2  
    The Doctor Quantime's Avatar
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    The angle, if you look at it at a slant the light is passing through more atoms and is being absorbed by electrons and hence losing energy-hence red colour.


    "If you wish to make an apple pie from scratch, you must first invent the universe". - Carl Sagan
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  4. #3  
    Forum Professor captaincaveman's Avatar
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    Quote Originally Posted by svwillmer
    The angle, if you look at it at a slant the light is passing through more atoms and is being absorbed by electrons and hence losing energy-hence red colour.
    thats not correct the reason is because The mirrored
    "grooves" act as a reflection diffraction grating, causing interference
    patterns in the reflected light.

    heres an article on it

    http://electronics.howstuffworks.com/question52.htm
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  5. #4  
    The Doctor Quantime's Avatar
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    Not bad to say I theorised that response with the knowledge I had.

    I'm still right though. The light being at an angle does factor.
    "If you wish to make an apple pie from scratch, you must first invent the universe". - Carl Sagan
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  6. #5  
    Forum Professor captaincaveman's Avatar
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    Quote Originally Posted by svwillmer
    Not bad to say I theorised that response with the knowledge I had.

    I'm still right though. The light being at an angle does factor.
    theanswers in the question, the fact that thereis a spectrum of colour on acd, negates the "red" comment :wink:
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  7. #6  
    The Doctor Quantime's Avatar
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    Quote Originally Posted by captaincaveman
    Quote Originally Posted by svwillmer
    Not bad to say I theorised that response with the knowledge I had.

    I'm still right though. The light being at an angle does factor.
    theanswers in the question, the fact that thereis a spectrum of colour on acd, negates the "red" comment :wink:
    Well you know what I meant I wasn't far off.
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  8. #7  
    The Doctor Quantime's Avatar
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    Caveman how does it define the color? Where does the colour come from?
    "If you wish to make an apple pie from scratch, you must first invent the universe". - Carl Sagan
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  9. #8  
    Forum Professor captaincaveman's Avatar
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    Quote Originally Posted by svwillmer
    Caveman how does it define the color? Where does the colour come from?
    here something for ya,it'll explain it clearer than me :-D

    http://www.devx.com/projectcool/Article/19954
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  10. #9  
    Forum Masters Degree SuperNatendo's Avatar
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    The white light is refracted by the cd and makes the seperate colors of the light appear
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  11. #10  
    Forum Freshman Rye Rye's Avatar
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    The reason that the CD splits the light spectum, is because it slows light down, however does not stop it entirely. It does this in order to isolate red light, which is read by photo sensors.

    Since you are looking at a four-dimensional phenomenon (light) on a two dimension surface, the numbr lines you see are actually represent the roots of the angles of the passing light beems on the CDs surface.

    For example, if you hole the cd flat directly in front of your eyes, youll see two multicolored lines. This is just the square root of the passing beams angle. Tilt it a little more, youll see three lines, the third root of the angle passing beams, four...n lines, etc.

    Basically the n number lines you are seeing is the nth root of the angles of the passing light over the surface, the color represents the direction from which the light is approaching.

    The colors are due light being slowed, but not stopped by the CD. The CD IS semi-transparent to isolate red.
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