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Good explanation, that made me think a bit… First thought was ‘so why is glass opaque to infra-red AND ultra-violet but NOT visible??’. He explains that you need high-energy photons to cause absorption but low-energy IR photons are absorbed too…
Thinking a bit more: photons have to promote electrons between energy levels, so there must be available transitions between energy levels corresponding to IR and UV, but no transitions corresponding to visible photon energies.
Does bonding change the available levels? I guess it often does as colour changes during reactions are common. Can anyone with a little more quantum chemistry knowledge elaborate?
Great series of videos though – hard to top the periodic table of videos but these are doing a good job!
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These guys are absolutely brilliant. I think ive watched every sixtysymbols video.
Comment by addidis — February 25, 2011 @ 4:49 pm
Good explanation, that made me think a bit… First thought was ‘so why is glass opaque to infra-red AND ultra-violet but NOT visible??’. He explains that you need high-energy photons to cause absorption but low-energy IR photons are absorbed too…
Thinking a bit more: photons have to promote electrons between energy levels, so there must be available transitions between energy levels corresponding to IR and UV, but no transitions corresponding to visible photon energies.
Does bonding change the available levels? I guess it often does as colour changes during reactions are common. Can anyone with a little more quantum chemistry knowledge elaborate?
Great series of videos though – hard to top the periodic table of videos but these are doing a good job!
Comment by Steve — February 25, 2011 @ 5:01 pm
Thanks for the discovery!
Comment by kangooooooo — March 2, 2011 @ 8:44 pm