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How does light illuminate objects? (help me in a debate)

  1. Sep 20, 2010 #1
    How does light "illuminate" objects? (help me in a debate)

    Hello,

    I'm curious as to how light illuminates an object. To be more specific how does light allow give an outline to a body?

    Can an seemingly physical object be visible to the naked eye and at the same time be non-physical? I know this seems like a nonsensical question, but I'm having a debate with a person and need 'backup' so to speak. I'm trying to make the claim that if a non-physical entity is visible, then the object can not be non-physical, because the wavelength of the light would not be interrupted.

    If anyone can provide a link or source I would appreciate it greatly.

    I know that the wavelength of the light an object is viewed under is somehow a limiting factor in resolution. However, I'm not sure if this relates to my question or not.

    P.S. I may have made spelling mistakes, but I'm in a rush, so please forgive me.
     
  2. jcsd
  3. Sep 20, 2010 #2
    Re: How does light "illuminate" objects? (help me in a debate)

    A "seemingly physical object" such as a... ?

    A "non-physical entity" such as a... ?
     
  4. Sep 20, 2010 #3

    Drakkith

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    Staff: Mentor

    Re: How does light "illuminate" objects? (help me in a debate)

    Light bounces off of objects that are not transparent/translucent and your eye receives the light and process it to form a visual image.

    It is possible to have an "invisible" object that is 100% real, but that would involve a variety of tricks and optical effects.

    Also, I'm not sure what you mean by a non-physical entity? Non physical to me implies that it has no substance, it isnt made up of matter or energy, as both are physical to me. In the context of physics and science, there isn't anything that can exist and be non-physical.

    Now if you want to talk about ghosts or something, that is not in the realm of science and no one can give you an answer for.
     
  5. Sep 20, 2010 #4
    Re: How does light "illuminate" objects? (help me in a debate)

    It's a long story...

    Thanks Drakkith.
     
  6. Sep 22, 2010 #5
    Re: How does light "illuminate" objects? (help me in a debate)

    Light can be generated directly or reflected off of material objects with varying wavelength absorption and reflection. Lightning or sparks, for example are visible but not because light is reflecting off matter. Likewise, a flame (I believe) is visible because the radiation emitted by the combustion is refracting around the air as it rises turbulently, so that is in one sense physical in that the air is physical, but it's not like the light of the flame is generated by the air itself. Actually, I might be wrong and it is the combustion of flammable gasses themselves as they rise that create the visible flame. Maybe someone else can clear this up.

    What about a rainbow, though? Rainbows are caused by an array of water-droplets acting as prisms. So, although there are physical water droplets involved, the bands of color visible are not the droplets themselves, b/c from another angle they would not appear.
     
  7. Sep 22, 2010 #6
    Re: How does light "illuminate" objects? (help me in a debate)

    I think he means like a holographic projection.
    holograph-final-1.jpg

    such things are impossible, i believe
     
  8. Sep 23, 2010 #7
    Re: How does light "illuminate" objects? (help me in a debate)

    Certainly impossible with only one projector.
     
  9. Sep 23, 2010 #8
    Re: How does light "illuminate" objects? (help me in a debate)

    How would it be possible, even with a million projectors, if you were, say, in a vacuum?
     
  10. Sep 23, 2010 #9
  11. Sep 23, 2010 #10

    Drakkith

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    Staff: Mentor

    Re: How does light "illuminate" objects? (help me in a debate)

    Holography, mirages, and other optical tricks are all caused by physical phenomena. Now, I'm assuming a "Non-Physical Entity" is something like a ghost?
     
  12. Sep 23, 2010 #11
    Re: How does light "illuminate" objects? (help me in a debate)

    It should be possible to do some elementary shapes with a well-chosen gas, and a few intersecting, well-shaped beams (at least a cube!).

    Anyway, here's something nice:

    http://www.optigone.com/3D_hologram.htm [Broken]
    http://www.tradeshowhologram.com/video.html
     
    Last edited by a moderator: May 4, 2017
  13. Sep 24, 2010 #12
    Re: How does light "illuminate" objects? (help me in a debate)

    Well you would need a well-chosen gas.. in that case, you could cram, say, 20 projectors into one encasing and walla - hologram
     
    Last edited by a moderator: May 4, 2017
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