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Old Jun 1st 2015, 04:13 AM   #1
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How do we see anything?

Hello

How are my eyes able to know the direction from where photons are coming when they are trying to interpret what we see? Isn't that the only way my eyes could distinguish objects?

Shouldn't we be simply seeing a "snowstorm" in each of our eyes?

As the picture shows, photons bounce off from objects into random directions so how are our eyes able to see anything?

Thanks in advance!
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Old Jun 1st 2015, 05:18 AM   #2
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Photons don't bounce off the photoreceptors at the back of the eye, they are absorbed.

Due to that absorbtion, the energy of the photons power an electrochemical signal to the optic nerve.

As to direction , you have a mozaic of photreceptors at the back of the eye and the pattern of light is translated into a pattern of electrical signals in the photoreceptor.

Each eye produces a 2D pattern that is slight different because the eyes are in different positions in the head

The brain interprets the different patterns and computes the composite 3D image as a result.

Near magic isn't it?

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Old Jun 1st 2015, 06:26 AM   #3
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Jireat - I think what you're missing is that while photons generally scatter in all directions off an object, they then travel in a straight line from the object, and thus what you see are only those photons that have traveled in a straight line from the object to your eye. The lens of your eye then focuses those photons that are coming from the object you are looking at onto the optic receptors in your eye. All the other photons that come off the object that are traveling in a straight line somewhere other than to your eye are in a sense "wasted," in that your eye doesn't see them. Consider for example a crowd of people watching a soccer game: a very small fraction of the photons that come off the soccer ball will hit the eye of person A and be seen by him, and a different small set of photons will hit the eye of person B and be seen by him, etc. Thus each person in the crowd "sees" a different set of photons.

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Old Jun 1st 2015, 06:28 AM   #4
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Good point ChipB
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Old Jun 2nd 2015, 06:36 AM   #5
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Originally Posted by ChipB View Post
Jireat - I think what you're missing is that while photons generally scatter in all directions off an object, they then travel in a straight line from the object, and thus what you see are only those photons that have traveled in a straight line from the object to your eye. The lens of your eye then focuses those photons that are coming from the object you are looking at onto the optic receptors in your eye. All the other photons that come off the object that are traveling in a straight line somewhere other than to your eye are in a sense "wasted," in that your eye doesn't see them. Consider for example a crowd of people watching a soccer game: a very small fraction of the photons that come off the soccer ball will hit the eye of person A and be seen by him, and a different small set of photons will hit the eye of person B and be seen by him, etc. Thus each person in the crowd "sees" a different set of photons.
I think it makes sense. Thank you very much!
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Old Jun 5th 2015, 02:05 AM   #6
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There are 2 component known as eyes,which are very important part of body.We can see every thing with the help of them.And this system is also called "Human Visual System" and only "see" after our brains interpret what's sent to them from our eyes.
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Old Aug 1st 2015, 03:41 AM   #7
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Adding to the above, light coming into the eye first passes through a lens. The lens changes the direction of the light. This enables an image of what you're looking at to appear on your retina where there is an array of cells that detect light. Since you have two eyes you see two slightly different images. The closer the object that your looking at is to you the more your mind is able to put it all together into a three dimensional view.
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Old Dec 26th 2015, 08:59 AM   #8
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Binocular Vision

It is a popular misconception that two eyes are neccesary to view a 3-D world. Ask anybody who has lost the use one eye.

Someone such as me for instance.

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Old Dec 26th 2015, 06:43 PM   #9
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Originally Posted by kengreen View Post
It is a popular misconception that two eyes are neccesary to view a 3-D world. Ask anybody who has lost the use one eye.

Someone such as me for instance.

Ken Green
I know of nobody that has said that you need two eyes to view a 3D world. Two eyes are only required to have depth perception. People can sort of have a depth perception with only one eye when the know the sizes and distances of the objects in their field of sight.
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Old Dec 26th 2015, 07:10 PM   #10
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There is also some depth perception afforded by the focal length of the lens in the eye.
It is perhaps something I have noticed more as I get older, and the lenses in my eyes become stiffer, but I can definitely feel the difference in effort required to focus at different distances.

It is the disconnect between the depth perception from the focal distance of lens and the depth perception from binocular vision that can give some people headaches in 3D movies.
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