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Light and Vision: Photon Direction

  1. Dec 16, 2009 #1
    How is it that light disperses from a point source (like a pinhole w/ a light shining through). From my understanding, photons disperses in all directions at all angles. So than how is it that an eye can differentiate that point from all the other points light around it (say there was another pin hole in a different area of the field of view). Would not the complete dispersal from one point of light hit every photoreceptor cell? And if so, how would it differentiate that stimulus from another point of light?
    Thanks very much.
  2. jcsd
  3. Dec 16, 2009 #2


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    That's what the lens of the eye is for. It converges the light from each point source to a single point on the retina.
  4. Dec 16, 2009 #3


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    It is the angle of the rays coming in to your eye that identifies the direction to you.

    Think about what you're seeing right now. There's a light ray coming from a window in your peripheral vision. It impinges on your eye near the edge of your cornea and directed into your pupil where it impinges on your retina way over near the edge. A stimulus received at that point on your retina appears in your vision as a source of light in your preipheral vision.
  5. Dec 16, 2009 #4
    Still not sure i understand. Let me try illustrating my understanding, and then correct me one how terribly misinformed i am.

    In the attachment i did a rough representation of what i'm talking about. If two points of emitting light are next to each other and near the eye, wont their photons be crossing paths, eventually striking same receptors?
    I mean, one point of light does not transmit through the eye in only one direction/angle, does it?

    Attached Files:

  6. Dec 16, 2009 #5


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    The purpose of a lens component is that it takes divergent rays coming from a single distant source and focusses them at a point.

    See diagram.

    Attached Files:

    Last edited: Dec 16, 2009
  7. Dec 18, 2009 #6
    I think i get it. Thats pretty amazing. Thanks very much!!
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