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Sun + Magnifying Glass = ?mw

caleb said:
i wana get some massive mirror thing and annoy people over 3km away.
does anyone know what something like this is called.
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TDNS- That Damn Neighbor Syndrome

-Mark
 






very "buildable" and adjustable the second lens makes the converging light into a parallel  beam shape with a swivel mirror you could possibly reach 2500F.
not sure if the second lens would melt though.
 
is the swivel thing to point it around and annoy people... :)
or burn a house down... over 2km... ::)
 
parallel
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You must realize that there is no parallelism. ::)

..because that would be 0 divergence, and we all know you can't have 0 divergence, it has been talked about so many times on this forum, there's no point in explaining why again.Further more, since we all know you can't have 0 divergence, and that all light diverges from it's source, we know incoherent light (like sunlight, like in your example) diverges even more, so you won't be able to have a usable beam to actually heat things up to 9000F much farther than a few inches from the second lens(not to mention the mirror).
 
lol I know and no way will it go hotter that maybe 2500F (iI wanted my idea to sound better so I exaggerated a small bit)
 
I can pop balloons in under a quarter-second with a 4 inch magnifying glass.  :D Last Friday.  ;D
 
omg in two weeks when our new big screen gets hear were throwign ours out i had no idea thease were in them ill have ot take it out
 
I picked up a 38" Fresnel on eBay a few weeks ago. I couldn't find one of the really big 59"ones anywhere so I broke down and spent probably more than I should have. These things are totally awesome! We were melting concrete, pennies and beer bottles with it last week while waiting for the mash to finish during our weekly brew session.

A couple things to keep in mind though. As in a previous post, these are built as either a linear lens or a spot lens. It is the spot lens you want as you can get it to focus fairly tightly. A stand is also a must as it is unwieldy to hold the thing perfectly focused. And make sure you point the rough side (the one that has the concentric circles etched into it) toward the sun. Works much better that way.

One more important tip. I was so excited when it arrived - and so impatient to burn something - that the shipping box it came in became its first victim. Now I have to be really careful not to let the thing lay around during the day as even a little bit of sunlight will generate a tremendous amount of heat. (I lit part of my field on fire by letting myself get distracted.) The good news is my wife wants me  to buy some more and try to heat the pool with them this winter  ;)
 
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