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Why??!?!!!!

chipdouglas

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try this with the tip of a lit cigar and a 405nm. the light directly over the cherry of the cigar turns turquois.

michael.
 

Asherz

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I'm gonna go with the heat causing all the particles in the air to rise and the beam there for not showing as there's nothing to reflect of instead of the mirage theory.

The reason I went for the former over the later theory is the mirage whilst it could interfere with the laser as hot air has a lower refractive index than cold air, surely would also cause ALL the light you see in the region to be interfered with, not just the laser, the entire background which is also just light would be interfered with?

It doesn't seem right that just the laser would be affected, and not all the other light.
 

Ra1nfade

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LOL, yeah what can I say i've always been interested in lasers and lights. As soon as I seen that people were custom machining their own parts I was hooked. :D

They also said the same thing when I was working with CAD/CAM systems and my colors were all messed up lol
 

daguin

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Daguin... look again, at about 00:33 or so in the vid.

Briefly, OVER THE FLAME, (not IN the flame), there IS an odd "segment" that seems to be "chopped out" of the beam.

It IS weird, once you notice it.

The "flame" is significantly larger than the visible light you can see from it.
The "visible" flame and the "thermal" flame are NOT the same thing.
You are restricting your judgement to what you can "see."

Not all phenomenon are visible ;)

I guess it would have been more correct to say that there are no particles floating around inside the thermal limits of the combustion event to reflect or scatter the light in the direction of your eye.
However, I usually sound pompous enough already :whistle:

Peace,
dave
 
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The "flame" is significantly larger than the visible light you can see from it.
The "visible" flame and the "thermal" flame are NOT the same thing.
You are restricting your judgement to what you can "see."

Not all phenomenon are visible ;)

I guess it would have been more correct to say that there are no particles floating around inside the thermal limits of the combustion event to reflect or scatter the light in the direction of your eye.
However, I usually sound pompous enough already :whistle:

Peace,
dave
So is there a mini vaccuum there? Because there either has to be something or nothing.. and "something" would still reflect or distort the light to a [albeit possibly smaller] certain degree.
 

qumefox

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No vacuum. The flame event is just displacing the particulate in the air. No particulate means you can't see the beam even though it's still there. The issue isn't as noticable with 445 or 405 due to the fact that in dark conditions with enough power for burning, reyleigh scattering is enough for the beam to still be visible. Which is why I said I didn't notice it earlier when I tried it.
 
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No vacuum. The flame event is just displacing the particulate in the air. No particulate means you can't see the beam even though it's still there. The issue isn't as noticable with 445 or 405 due to the fact that in dark conditions with enough power for burning, reyleigh scattering is enough for the beam to still be visible. Which is why I said I didn't notice it earlier when I tried it.
I've still seen this effect with a 1.5W pure green laser though! With smoke in the room!
 

BShanahan14rulz

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The "beam" that you see isn't photons, its just light hitting crap floating in the air. Combusting these particles turns 'em into gas, kind of like smaller particles, way way way smaller. Less scattering.

Ok, I lied. You see, the beam is created when laser light stimulates gaseous emissions from the rear end of chip weevils. Fire kills chip weevils, and dead chip weevils can't fart.
 

daguin

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I don't know any clearer way to put it.

Nothing to reflect or scatter does NOT equal nothing there.

Because you cannot see something does not mean that nothing is there.
Try holding your finger above the flame, outside of the visible light. You will probably discover that the "flame" goes well beyond the edges of what you can see ;)

It is not a vacuum. There are plenty of gasses present. The gasses are just not reflecting or scattering the light in the direction of your eye.

Peace,
dave

**EDIT** -- From BShanahan14rulz above: the beam is created when laser light stimulates gaseous emissions from the rear end of chip weevils. Fire kills chip weevils, and dead chip weevils can't fart.

I'm going with this theory from now on.
 
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