# Laser burning. Distance?



## Genxsis (Aug 25, 2007)

Totally new to the world of high powered lasers!

I've been hearing about these lasers that can cut through electrical tape, pop balloons, etc. But up to what distances? I'm asking because I wonder whether or not if I were to have one of these and be shining it around outdoors and aim it at a group of trees 150 or 200 yards off in the distance, it could start a fire.

Do lasers lose burning/cutting ability with distance? The videos I've seen online show matches being lit, etc. at distances of 5 feet or so. How far away could it do something like that?


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## Ashton (Aug 25, 2007)

Did you ever use a manigying glass to start fires or fry ants as a kid? a laser works the same way, it must be focused. The pwoer lies at hte focal point of hte laser. So, technicallt no, you *can* focus one to whatever distance you want, but realistically, yes, it will. However enough pwoer and even when it's not in perfect focus it will do some serious damage (though we're talking abour 500mw and up) You could also set up a series of culminators and extend the distance as far as you want, provieded they're in a line.

You really need to say what kind of laser you want, Handhelds are gennerally limited to a MAX of 2watt (IR) or 500-700mw (green/red) while labbies can go all the way to 80watt and industrial lasers can enter the megawatt, or even gigawatt or terawatt range.


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## Genxsis (Aug 27, 2007)

Focused? I thought lasers were already focused into a tight beam from the time the light leaves the emitter. So then wouldn't the energy of the beam be the same at any distance?


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## Gunner12 (Aug 27, 2007)

Some of a laser's energy is diffused by the air and particles in the air.

In theory, a laser would be perfectly focused but in real life, this is not true. Some badly focused lasers spread to a inch wide beam at a relatively short distance.


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## Genxsis (Aug 27, 2007)

:thumbsdow


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## comozo (Aug 27, 2007)

Genxsis said:


> Ok, so how far away would a typical, say 175mw laser pointer be able to start a fire if directed at an object in the outdoors? This is assuming that it was a properly focused one.
> 
> BTW, I could imagine plenty of abuse here. Someone beaming their neighbor in the back and then turns it off just as the neighbor turns around to see what's stinging him. Or maybe arsonists in Greece starting fires all over the place, for whatever reason.....:mecry:



That question is not as simple as you may think it is


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## picrthis (Aug 27, 2007)

Genxsis said:


> Ok, so how far away would a typical, say 175mw laser pointer be able to start a fire if directed at an object in the outdoors? This is assuming that it was a properly focused one.
> 
> BTW, I could imagine plenty of abuse here. Someone beaming their neighbor in the back and then turns it off just as the neighbor turns around to see what's stinging him. Or maybe arsonists in Greece starting fires all over the place, for whatever reason.....:mecry:


Not so easily done and the object/person and Laser would have to not move at all.


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## photonxiii (Sep 12, 2007)

Genxsis said:


> Ok, so how far away would a typical, say 175mw laser pointer be able to start a fire if directed at an object in the outdoors? This is assuming that it was a properly focused one.
> 
> BTW, I could imagine plenty of abuse here. Someone beaming their neighbor in the back and then turns it off just as the neighbor turns around to see what's stinging him. Or maybe arsonists in Greece starting fires all over the place, for whatever reason.....:mecry:



Hmmm...with a 175mW you'd have to be _really_ close...say, maybe within 4 feet or less. :laughing: And it depends on the object, most of the time you'll just scorch 'em...a little. Generally speaking, current laser pointers just don't have enough power to set anything on fire... yet. 

As for beaming your neighbor...I do that to my officemates with my 200mW, works like a charm. :devil:


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## steve-o2 (Sep 18, 2007)

Diode lasers have lenses to focus the beam creating a "beam waist" which is the narrowest (and most powerful) point, unlike most gas lasers that have no lenses and continuous divergence. The farther away from the source in either case, the more divergence and less power (burning ability.) I have seen a 3+Watt green dpss smoke a white pizza box at >10 feet though:thumbsup: A 20 Watt Krypton can toast mosquitos who fly through the beam at quite a long distance though due to the sheer power and beam diameter.


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## steluta (Sep 19, 2007)

SPAMMER removed.
bernhardhttp://www.pharmasport.org/


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