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How does a photon actually carry an image

  1. Feb 4, 2009 #1
    How does a photon actually "carry" an image

    i understand how we see colours the photon hits an atom which gives out a photon with a different wavelength and this photon collides with chemicals in the eye etc etc.
    but how is it that we actually are able to see what the photon has collided with is it to do with multiple photons and how they "bounce" off the object and how our brains intepret these?

    thanks in advance
    matt
     
  2. jcsd
  3. Feb 4, 2009 #2
    Re: How does a photon actually "carry" an image

    Photons do not carry images. You can see photons as individual 'pixels': many photons combined (of the right 'color' (or wavelength)) form an image on your retina, which is interpreted by your brain.
     
  4. Feb 5, 2009 #3
    Re: How does a photon actually "carry" an image

    I understand that the convex lens produces a real image on the retina, but I'm confused about how the brain can be informed which location on the retina has been illuminated by which color and intensity of light. Does every photosensitive cell on the retina have its own nerve pathway to the brain? But people speak of the optic nerve in the singular.
     
  5. Feb 6, 2009 #4
  6. Feb 6, 2009 #5

    jambaugh

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    Re: How does a photon actually "carry" an image

    Each eye is measuring the direction of motion of the incomming photons based on where on the retina they hit. This plus the fact that the photon is hitting the eye and not your nose or the moon tells us the direction of that point on the object where the photon was emitted. Add binocular vision and we get a rough estimate of distance as well.

    But a single photon doesn't an image make. Rather it is a whole bunch of them each carrying a little bit of information.

    You should look at the technique of ray tracing in computer graphics.
     
  7. Feb 6, 2009 #6
    Re: How does a photon actually "carry" an image

    Seeing images of objects has nothing to do with the quantum properties of light, at this scale it is much more realistic to think of light as a classical electromagnetic wave.
     
  8. Feb 6, 2009 #7
    Re: How does a photon actually "carry" an image

    The retina is actually a part of the brain. The optic nerve is a nerve bundle containing more than a million nerve fibers.
     
  9. Feb 6, 2009 #8
    Re: How does a photon actually "carry" an image

    The pixels metaphore is a good one, how the brain actually pixelates into an image in our visual cortex is still a bit of a mystery, but as said it's just the amount of different light and wavelengths that give us an overall image, there' nothing inherent in photons themselves. Black as a colour is generally the absence of light which is why when we turn the light off everything is black. The other colours are all just RGY/B mixes.

    Recently they have mapped specific shapes in say letters onto the brain, but this still leaves as many questions as it answers, particularly in the fields of philosophy which deal with the hard problem, and neuroscience generally.

    http://en.wikipedia.org/wiki/Eye

    http://en.wikipedia.org/wiki/Human_eye

    Wiki has a basic overview if you're interested.
     
  10. Feb 7, 2009 #9
    Re: How does a photon actually "carry" an image

    Would it be possible to physically alter the eyes/brain so that we could observe higher/lower frequencies of light which in turn would allow us to discover new colors?
     
  11. Feb 7, 2009 #10
    Re: How does a photon actually "carry" an image

    We already do with IR googles and UV goggles, those are some of the "colours" that some animals can see, for example goldfish can see into both UV and IR IIRC. Bees sight is shifted into the blue for example and UV, so flowers look very different to them.

    [​IMG]
     
  12. Feb 7, 2009 #11
    Re: How does a photon actually "carry" an image

    I realize that, but all those goggles do is transforming those 'other' colors to colors *we* can see, right? I.e. we're still not seeing the actual colors.
     
  13. Feb 7, 2009 #12
    Re: How does a photon actually "carry" an image

    You can mimic what it would look like by shifting the colours somewhat, but no of course we couldn't see exactly what they see, and there doesn't seem much point in doing so, when you can utilise such "colours" without invasive procedures. You could do it though in theory.

    Think about predator when it takes off its IR goggles and sees only in IR, it's like black and white but with Red and white. Why bother under utilising the spectrum. Of course you could in theory make everyone see UV and IR and even more high or low energy EM, like Jordy Laforge in Star Trek, I don't see that as particularly far fetched at all, whether it would be of any more use than an external device is another matter?

    http://images.google.co.uk/imgres?i...hat+flowers+look+like+to+bees&um=1&hl=en&sa=G

    A bees eye view.
     
    Last edited: Feb 7, 2009
  14. Feb 7, 2009 #13
    Re: How does a photon actually "carry" an image

    Wouldn't it be sort of beneficial, though? I mean, if we were to genetically modify ourselves so that we could see heat radiation or even gamma rays, we wouldn't even devices like geiger counters and such. Though I suppose it would perhaps become very distracting considering all the stuff that goes on in the background that we normally don't see.
     
  15. Feb 7, 2009 #14
    Re: How does a photon actually "carry" an image

    It would be good if you could turn modes on and off, mind you I'd still personally prefer a sort of visor dealy.
     
  16. Feb 7, 2009 #15

    Hootenanny

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    Re: How does a photon actually "carry" an image

    Modifying the rods and cones in our eyes to respond to additional wavelengths/energies would be one thing. Modifying our brains to interpret this information is a completely different task, one I would venture that would be impossible.
     
  17. Feb 7, 2009 #16
    Re: How does a photon actually "carry" an image

    I always hate using the word impossible, but I have to agree it would takes some serious genetic engineering to actually make us see it, rather than see it in a fashion that was visible to us, of course not even Jordies visor does that.
     
  18. Feb 7, 2009 #17
    Re: How does a photon actually "carry" an image

    Hmm this sounds a bit like a philosophy problem that it's impossible to 'see' reality because everything is just interpreted by a sensing system. Also nobody knows if someone else's blue 'looks' red or visa-versa...

    On to the logistical problems, seeing heat might be possible but short wavelength gamma rays pretty much go through anything, so they'd be pretty difficult to detect. Also if the wavelength of radiation is larger than the pupil then it wont reach the retina...
     
  19. Feb 7, 2009 #18
    Re: How does a photon actually "carry" an image

    It is a philosophical area, see the hard problem, consciousness issues and so on for more details. Obviously this is not the place for those discussions.

    But The Threefold Chord: Hilary Putnam is a good overview of the problems facing philosophy of science in this area. And googling qualia wouldn't go a miss.
     
  20. Feb 7, 2009 #19
    Re: How does a photon actually "carry" an image

    For all we know, the brain's conceptual color spectrum could be extended by growing some new meat. It's an unknown, but the kind of peripheral thing that might in fact be simple.
     
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