What happens to light after it hits the retina and initiates a nerve signal?



I’m labelling this as physics rather than biology because **I’m not asking about how our body uses the light to create an electric signal, instead I’m interested in where the light that has entered the eye and hit the retina then goes after the process?**

I hope that’s clear.

In: Physics

The light is absorbed to create that electrical signal and to my recollection it also generates a small amount of heat. So the photon itself is converted entirely to heat and (electrical) energy, there is no “light” left to go anywhere, it’s in a different form altogether.

Light that isn’t absorbed in this way is reflected back out, which is how we can see eyes and even into the eye with the right equipment.

It’s gone. It’s absorbed by the retina. That’s how vision works in the first place. You can’t not ask about how how the light creates a signal because it’s the same thing as what you’re asking.

it is absorbed by the molecules in our rod/cone cells, same as anything else. photons are gone once they are absorbed and that light doesn’t exist anymore.

Just to build on what everyone else is saying:

If you’re in the northern hemisphere, some clear night this summer look at a star map, then go find the Northern Cross and look at Deneb at the top of it.

Somewhere in the heart of Deneb, there are fusion reactions going on. I don’t know what the internal dynamics of a giant like Deneb are, but let’s just say that these fusion reactions lead eventually to a photon streaming off of the surface of Deneb.

This happened around 600BC. Since then it’s been flying through space.

Go out and look at it, and just by the act of seeing it you’re taking this little bundle of energy, forged in the heart of a giant star, flung off its skin, and absorbing it with your retina. Somewhere inside Deneb, atoms fused and mass was lost, and for however brief a time that energy was part of you.