title is self explanatory.
In: Planetary Science
I am going to assume you are talking about the photons that actually go to the inside of your eye. The photons that hit most of the outside of your eye are either reflected or absorbed with nothing too interesting happening. The reflection part is why you can see somebody else’s eyes.
Since you are an adult on reddit, you probably remember from some science class or another that on the back of your eyeball, there is a layer of cells that are called rods or cones. These cells are sensitive to light, and they’re the ones that actually deal with photons.
Let’s say a photon enters your eyeball and successfully hits the back of your eye. This is the first step in producing an image. What happens to it? The rod cells and cone cells that line the back of your eye have special proteins in them. These proteins can actually absorb the energy of the photon and use it to change shape. When the protein that absorbs the photon changes shape, it actually pushes on the membrane of the cell that surrounds it. That triggers a very long and complicated series of steps that might ultimately end up in a signal being sent to your brain that indicates there was light from that cell or a nearby cell (the reason I say a nearby cell is that your nervous system actually combines the signal from several adjacent cells).
So what happens to the photon that enters your eye? It is destroyed. It hits the protein, carrying its energy. It’s absorbed by the protein. The energy that it had is used up to convert that special protein into a different physical shape. So it’s gone.
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