Blue vs. green, how far goes the beam?

[BShanahan14rulz]

I would guess the green, assuming same divergence, same power output, and same conditions. If you have x particles in the way, I would guess that whichever has more photons would have higher chance of making it through. But stuff acts weird when you get to those small scales, so I'm probably way off, not to mention it also depends heavily on the type of particles, size, shape, etc.

Interesting thought exercise.

 

[AnselmoFanZero]

*giggle*

 

[Encap]

It depends on the size and weight of the individual laser. Those little laser pointers that are used to put a red dot on the screen during a presentation can be carried around on a key-ring, and can go wherever the owner of the keys goes, whereas the multi-megawatt lasers used for astronomical probes are permanent fixtures in observatories, and can't travel at all once they're installed.

 

[AnselmoFanZero]

Eddy Murphy is a hamster compared to you my friend.

 

[BShanahan14rulz]

heh, I chuckled.

 

[Blarg King]

Perhaps this will help:

 

[DashApple]

Yeah I know. But how far will blue go?

51.456*Pi Miles + one banana .

 

[Alaskan]

It's for signaling UFO's, that's why the distance.

 

[zyxwv99]

The question you have asked is pretty complicated. The most I can do is provide you with some data to help figure it out. First, according to CIE 2000 the photopic sensitivity of the human eye (daytime color vision) is 88.49624 % of maximum at 532 nm, 3.288368 % at 447 nm. (100% is at 555 nm.) As a result, 447 nm blue needs to be 26.9119028 times as bright at 532 nm green to have the same apparent brightness.

This does not take into account the fact that the two kinds of lasers are constructed differently and have different optics, beam divergence, etc.

Then there's the issue of atmosphere. 50% of the atmosphere is below 5.6 km. If you're pointing a laser up into space, the amount of atmosphere the beam passes through is the equivalent of 11.2 km at sea level. It might simplify things to pick an altitude, such as sea level, and just stick with that.

 

[Atomicrox]

Strangely the data on that PDF is the same as the older (and less accurate) 1931 data...

 

[zyxwv99]

Strangely the data on that PDF is the same as the older (and less accurate) 1931 data...

Good catch! I forgot that the CIE still considers their 1931 standard "definitive." The actual number for 447 should be 4.41546% (extrapolating from 445 and 450 values) in which case the laser only needs to be 20 times as powerful as 532 nm, not 27 times.

 

[AstroLaser]

I don't know exactly how far the beam will go, but the low cost blue/violet laser I have does real good at charging up glow in the dark stuff from a distance !