What happens to light after it enters our eyes?

If I understand correctly, light is carried by photons. Light enters our eyes and is absorbed(?) by the rods and cones.

So, what happens to the photons afterwards? I started wondering what happens to that energy that is transmitted.

Please forgive the ignorance of this question.

I'll lend a helping hand.

www.aoa.org...
From the source.
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Vision begins when light rays are reflected off an object and enter the eyes through the cornea, the transparent outer covering of the eye. The cornea bends or refracts the rays that pass through a round hole called the pupil. The iris, or colored portion of the eye that surrounds the pupil, opens and closes (making the pupil bigger or smaller) to regulate the amount of light passing through. The light rays then pass through the lens, which actually changes shape so it can further bend the rays and focus them on the retina at the back of the eye. The retina is a thin layer of tissue at the back of the eye that contains millions of tiny light-sensing nerve cells called rods and cones, which are named for their distinct shapes. Cones are concentrated in the center of the retina, in an area called the macula. In bright light conditions, cones provide clear, sharp central vision and detect colors and fine details. Rods are located outside the macula and extend all the way to the outer edge of the retina. They provide peripheral or side vision. Rods also allow the eyes to detect motion and help us see in dim light and at night. These cells in the retina convert the light into electrical impulses. The optic nerve sends these impulses to the brain where an image is produced.
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Cheers.

For us to be able to detect light, the photons must interact and cause a chemical reaction. This happens when they are absorbed by a chemical called rhodopsin. The energy from the photons causes an alteration in the rhodopsin molecules and this process triggers a signal that is then sent along the optic nerve.

So, the photons that we use to actually "see" directly provide the energy to enable the process of sight to occur.

There are various references on the web but one that includes the above info can be found here

Mike

reply to post by qisoa



Apparently they "die" when they strike the Rods in our eyes and the energy wave is converted to heat which is then absorbed.

This lens (the Cornea) is being very carefully shaped by a small muscle so that the photon along with its traveling companions are aimed by refraction to a common point on the waiting retina. Here our photon ends it existence. It impacts on a light sensor called a "rod". The photon expends its energy and causes a complex photochemical reaction. Signals are sent via nerves behind the retina to the brain. Even as this visual information is being sent to the observer's brain it is being processed. What is finally received by the visual cortex is not a signal that says "light" but one that roughly says "dim pin-point". This incredible chain of events is rather amazing as the signal has not yet even reached the brain itself. What happens there is even more amazing. All the pin-points are put together in the visual cortex and an image is formed of a distant softly-glowing pin-wheel. The Andromeda Galaxy is reconstructed in the observer's mind from bits of light that were borne in the belly of stars two million years ago!

The Life of a Photon

reply to post by qisoa


Are you sure you really want to know? It will take a while. Some of the photons are reflected back. Shine a light into the swamp at night near where I live and you will see a bunch of glowing lights. Those are the eyes of the frogs, alligators and other creatures that have retinas reflecting light back. And the "redeye" you get with photos using flash? Those are photons coming back at the lens You are correct that some photons are absorbed. I get the feeling that by asking what happens to them, you are thinking of photons as tangible objects that have mass. Photons are massless, consisting only of energy. And compared to total energy budget of the human body, the energy of photons is almost incomprehensibly small. The energy of a photon is equal to the frequency times a constant called Planck's constant which is a really, really small number. It's 6.626x10^-34J-s. So only a very tiny bit of energy is absorbed in the eye. Of course, it is conserved .The energy from the photon is absorbed by a molecule in the rods and cones of the retina called rhodopsin, which is a covalently bound protein, bound to retinal. That puts the rhodopsin in a slightly energized state which initiates the signal transduction cascade that results in a signal being sent to the adjacent nerve cells. The optic nerve is sensitive enough to respond to membrane polarization resulting from a single photon.
Are you asleep yet? No? OK, maybe you want to know that on a very bright sunny day, solar irradiance is 900 to1300 Watts per square meter. If your pupils close down to 4mm, you will absorb or reflect (primarily absorb) 16 thousandths of a watt per eye.
Anyway, after being excited, the rhodopsin releases a retinal molecule the decays back to the ground state, releasing the absorbed energy as imperceptible heat.
I have a headache from all that. I apologize if I gave you one.

I find all of this to be very informative and interesting. I had wondered about the residual energy, etc.

I wonder if anybody has ever tried to reproduce the absorbative quality of the rods/cones and create an 'anti-mirror'. Since a mirror reflects all light, an anti-mirror would absorb all light. If that's a scientifically loony idea, I apologize. This is not my area of expertise.

Originally posted by qisoa
I find all of this to be very informative and interesting. I had wondered about the residual energy, etc.

I wonder if anybody has ever tried to reproduce the absorbative quality of the rods/cones and create an 'anti-mirror'. Since a mirror reflects all light, an anti-mirror would absorb all light. If that's a scientifically loony idea, I apologize. This is not my area of expertise.

Wouldn't that be the definition of the color black?

Wikipedia: Black is the color of objects that do not emit or reflect light in any part of the visible spectrum; they absorb all such frequencies of light.

...and there ya go.

Originally posted by Blarneystoner
Wouldn't that be the definition of the color black?

Well, I was thinking about that, but even with ablack object, we still can see the texture of the surface, be it cloth, ceramic, fur, whatever. What if the absorbing material absorbed absolutely all of the light, reflecting nothing?

Oh, wait...I guess I just described a black hole.

Originally posted by qisoa
I find all of this to be very informative and interesting. I had wondered about the residual energy, etc.

I wonder if anybody has ever tried to reproduce the absorbative quality of the rods/cones and create an 'anti-mirror'. Since a mirror reflects all light, an anti-mirror would absorb all light. If that's a scientifically loony idea, I apologize. This is not my area of expertise.

are you thinking about solar panels?

Originally posted by platipus

Originally posted by qisoa
I find all of this to be very informative and interesting. I had wondered about the residual energy, etc.

I wonder if anybody has ever tried to reproduce the absorbative quality of the rods/cones and create an 'anti-mirror'. Since a mirror reflects all light, an anti-mirror would absorb all light. If that's a scientifically loony idea, I apologize. This is not my area of expertise.

bsorb incident light, particularly if not polarized.

are you thinking about solar panels?

There is a subdiscipline in physics/optics which studies difraction gratings and their capacity to absorb light. Google "difraction grating.

Originally posted by qisoa

Originally posted by Blarneystoner
Wouldn't that be the definition of the color black?

Well, I was thinking about that, but even with ablack object, we still can see the texture of the surface, be it cloth, ceramic, fur, whatever. What if the absorbing material absorbed absolutely all of the light, reflecting nothing?

Oh, wait...I guess I just described a black hole.

In full disclosure, i am linking to my own blog here. This information was originally compiled by Zorgon, myself, and a few others (mostly Zorgon...he is a wizard like that). But it is a way to absorb light, and other EM energy. I cannot provide you the patent number. A savvy person could likely find it if they looked hard enough, given all the hints available between Zorgon and myself.

Invisibility and Cloaking

Not science fiction. Science fact. The secret is nanospheres, nested inside each other, each filled with a different material, to absorb a different spectrum. Then all you have to do is dissipate the energy (possibly the basis for the rumors of the plasma related tech with the stealth bomber?).