Originally posted by Andrew HamiltonI don't think there are any chemical reactions involved here.
I don’t know the answer to this question but what I do know might be a clue:
UV light consists of photons of higher energy than photons of visible light -so high that they tend to much more often ionise molecules by knocking off electrons off molecules and if the electron that is knocked off is that of a covalent bond then that generally means that ...[text shortened]... ides to specifically “changing their shape” although it may involve ionisation of the molecules.
Originally posted by mlpriorAs I was reading about photographic paper, I read that the silver atoms are not stable in this situation, but will spontaneously decompose unless you get a certain concentration of them (I think). The photographic paper has clusters of silver atoms which, because they are clustered, will not decompose.
The only information I can find indicates that Silver Halide crystals are used for the lenses.
When a photon hits a valence electron on the Silver Halide, it jumps the band gap into the conduction band. The electron travels until it is trapped by a shallow electron trap. The electron will reduce an interstitial silver ion to form atomic silver.
I have no idea how that reverses in the absense of UV light.
Originally posted by coquetteI think you just described fluorescence.
I think that this might be the answer, but someone really smart is going to have to let you know for sure.
The electrons are in orbits at the lowest, stable, energy state. When a UV photon comes along, it's like getting a swift kick and jumping up. That absorbed kick was invisible to the human eye because that range of energy doesn't serve any survival p ...[text shortened]... isible wavelength. That's because it's important for us to be able to see the object (ions).