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29/03/2009 03:15:47 »
I wonder if the greenhouse effect could be demonstrated in the lab. Would, say, a fish tank full of carbon dioxide get warmer than a similar tank of air when put in sunlight?
Neilep Level Member
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29/03/2009 11:36:28 »
Yes. One of the gadgets I use at work for measuring gases is a small container with a microphone in it. You fill it with the gas mixture you want to look at then shine a chopped beam of infra red on it ( "chopped" means it is switched on an off rapidly). As the IR is absorbed it heats the gas slightly and this makes the pressure rise. When the beam is switched off the pressure falls again. This alteration in ressure is picked up by the microphone and gives an indication of how much IR is absorbed and, from that you can work out what's in the gas mixture.
There's a bit more about the idea here.
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