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I am having a hard time in finding out what exact light media laser shows use. I am trying to build a laser show myself. I know that the laser light is reflected off these particles in such a way that that it makes the laser line "viewable" in all directions

Can somebody explain to me how exactly do the collection of particles make it viewable in all directions and what exact conditions are necessary? Does the angle of the incoming laser light matter? Does the size of the particles matter? Does the uniformity of how the particles are dispersed matter? Would water vapor work?

I have tried using a fog machine, but the red laser that I am using only reflects off of the fog particles in a way that makes it viewable only from a certain perspective. This would not be a good show to the people standing in one side of the room vs. another.

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Very neat question! +1 –  Marek Apr 11 '11 at 18:02
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Note that there is a huge difference between standard particles (elementary, atoms, or molecules) and droplets. Droplets are quite macroscopic and having a definite spherical shape, they would act as nontrivial optical medium (think about rainbows caused by water droplets) which could selectively prefer some directions. So fog is definitely not recommended.

On the other hand, if you have some gas at room temperature the scattering should be effectively classical and in all directions. So my recommendation would probably to use some non-lethal ;) gas.

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I am thinking about using water vapor made from a humidifier. Do you think this is a room temperature gas that would scatter light in all directions? –  QEntanglement Apr 11 '11 at 18:56
    
@QEntanglement: I guess it should work. But water vapor will condense on people, I am not sure you want that :) Still, have fun. –  Marek Apr 11 '11 at 20:32
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http://en.wikipedia.org/wiki/Theatrical_smoke_and_fog describes the methods used to create smoke. Also I think, in a room filled with people (like at evening parties), the humidity gets high enough to make light beams visible.

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