Ok, I realise the question title is kind of stupid. But I don't really know how to summarize it in one line as it's quite a weird, specific situation.
I have a lamp beside my bed on a shelf where I also leave a plastic bottle of water. I noticed recently that condensation builds up on the inside of the bottle (understandably). However, it only builds up on the side facing the lamp. Now there's virtually no heat coming from the lamp, but I thought it must be some tiny amount of heat that's just enough to cause it.
Last night, however, by pure fluke I left the bottle on a locker on the other side of the bed. I noticed this morning that there was a layer of condensation, again only on the side facing the lamp. Now this locker is right beside a radiator that has been pumping all night and is way to far away from the lamp for any tiny amount of heat it may generate to make a difference. So the only connection I can make is the light, which doesn't make any sense.
So my question really is: can anyone explain why the condensation always builds up on the side facing the light?