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How do our eyes "sense" photons?


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On This particular website:

http://science.howstuffworks.com/light4.htm

 

It states an interesting fact:

Any light that you see is made up of a collection of one or more photons propagating through space as electromagnetic waves. In total darkness, our eyes are actually able to sense single photons, but generally what we see in our daily lives comes to us in the form of zillions of photons produced by light sources and reflected off objects. If you look around you right now, there is probably a light source in the room producing photons, and objects in the room that reflect those photons. Your eyes absorb some of the photons flowing through the room, and that is how you see.
In TOTAL DARKNESS our eyes sense photons? How is that possible? Why would there be photons in COMPLETE DARKNESS? If you walk into the depths of a dark cave, you eyes will never adjust so that you can see where you are going. If our eyes sensed photons, wouldn't all animals be able to see in COMPLETE DARKNESS?
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we only sense photons of a specific frequency range, certain photo receptors in the "rods" and "Cones" of our eyes turn these into electrical signals that are passed down the optic nerve, these photo receptors rely upon photo-chemical reactions to generate these electric sigs, we get alot more photons hit/enter our eyes too, but these packets are out of our reaction range, ansd so remain uneffected :)

 

hope that helps a little?

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adding on to what yt2095 said:

 

these un-seeable photons are of too high or too low frequency [and wavelength] they include things like ultra-violet light, infa-red, and also; gamma rays, x-rays, radio-waves and micro-waves.

 

they all come from the elecrto-magnetic [EM] spectrum, we can only see the 'visible light' part of this spectrum.

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Firedragon, what they mean is that in the absense of any other photons we are able to sense a single one. I.e. if I sealed you up in a completely dark room and emitted a single photon, you would be able to tell.

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Not enitrely true. There is a threshold level needed to not only trigger the firing of neurons pre-optic nerve. There is also the threshold of detection in the visual cortex. I very much doubt a single photon would trigger a conscious recognition of the light source.

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that`s not "ADDING" to what I said, it`s at best expanding upon!
ah, whats the difference? its adding to the detail, expanding to the general purpose of your original post...

 

a single photon is quite small, whilsts theoretically you could see it, whethere your brain would register it as light is debateable due to the smallness of it.

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  • 4 weeks later...

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