Lasers, beams and colors...

[Hiemal]

Somewhat pointless thread?

I know Rayleigh scattering causes certain colors of lasers to have their beams visible...I know green, and pretty much anything below it their beams are visible.

Are red 650 nm and red 635 nm beams visible at all?

And I mean without fog or smoke...

 

[Sigurthr]

Only if the angle of observation is very acute from the target (dangerous). Though I haven't tested obscene powers yet.

 

[Ablaze]

If the air is dusty enough even a 5mw red laser will have a visible beam, and a bright enough laser will have a visible beam no matter what the wavelength, just due to reflections off of dust (or smog).