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I am wondering how cones (photoreceptors in the retina) can see color if colors are wavelengths but cones send signals when they absorb photons. Maybe by using the energy level (or only being sensitive to a specific energy level/range)? I suppose if you know E than the brain can provide the function for the wavelength like below? That's an assumption on my part that it's the brain doing the interpretation. Cameras use filters but the human eye seems doesn't seem to use that process other than that the fovea blocks some UV light. Certain cones are certainly sensitive to certain wavelengths, but how are they doing that by absorbing a photon? The energy of it seems to be the only thing that comes to mind.

$$E ~= ~ \frac { hc} { \lambda } $$

Chris
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p1l0t
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The interaction between photons and chemistry, eg, via atomic orbitals of single atoms, is a classic tool for understanding quantum mechanics, so there shouldn't be any surprises that the absorbing and emitting of photons is wavelength and photon-energy dependent. For example, this is used in studying spectra from stars, but in lots of other places too.

In the eye, there are opsins (light receptor proteins, e.g., rhodopsin), that absorb light and can consequently change structure, resulting in the eventual activation of neurons. Generally, what is a nice simple spectral line (for, eg, a single atom) will get broadened out in more complicated systems like a protein (ie, complication lead to interactions which lead to broadening). So it's not surprising that the opsins have a broad peak, centered at some wavelength and that peak falls off on either side (although with enough complication, like in a protein, anything can happen, but a single peak isn't a surprise). Given this, it's clear that tweaking the details of the opsins could give absorption peaks centered at different spectral locations, and, voilà,

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color vision!

tom10
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