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What happens at the point of intersection of 2 lasers. If 2 lasers of different colour intersect, what will be happening at the point of intersection? Won't colour mixing happen?? Won't that point where the lasers intersect be of different colour? For example if we use a green and a red laser then will not the point of intersection be yellow, if we use red and blue will not the point of intersection be magenta? The lasers are intersecting just in air.

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    $\begingroup$ Unless driven very hard, air is a linear optical medium. There will be no non-linear (mixing) of the two beams - they will propagate through each other with no other effects. $\endgroup$ – Jon Custer Sep 18 '15 at 13:18
  • $\begingroup$ If the beams are intersecting in air, then it makes no sense to talk about their color. Color is perceived in the brain, and (ideally) no light from the laser beam will enter your eye. If you put a screen there ... or if the room had a lot of dust floating around ... the situation would be different, and the perceived colors will mix just as they would from any light source. $\endgroup$ – garyp Sep 18 '15 at 15:05
  • $\begingroup$ thank you garyp, that is helpful. The lasers are in a room and there is dust in the air, not lot, but there is dust in the air, then what will happen?? $\endgroup$ – g g Sep 19 '15 at 5:57
  • $\begingroup$ garyp please this physics.stackexchange.com/a/164073/72692 $\endgroup$ – g g Sep 19 '15 at 6:12
  • $\begingroup$ is it possible to ask question from a specific user?? $\endgroup$ – g g Sep 19 '15 at 9:09
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Your question mixes two different notions of "color." There's a "physical" definition where it's used loosely to mean a pure frequency of light, as would come from a laser. There's also the view from human perception, which is the "intuitive" notion of color used in everyday language. They are not the same.

From the physical point of view, if the lasers just pass each other in air, they the electromagnetic field will obey linear superposition where they cross and the beams will continue on. At that point in space, the EM field is not acting as a pure "color" because there's the superposition happening. (At the other points along the laser beams, you could talk about single colors.)

The specific colors perceived by a person when mixing light that you mentioned are an effect both of the physical light and the way that the eye detects color. That's specific to humans though (and obviously different for, say, color blind humans), and is based on us having three different types of color receptors in our eyes. If you put a screen at the point where the lasers intersect most people (i.e. not color blind) will see the colors that you described, but that's because the eye cannot distinguish between getting a mix of photons in "green and red" from getting a single stream of photons at a pure color "yellow" not because the EM waves are somehow changed by the "mixing."

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  • $\begingroup$ @gg Great. If you think the answer is what you needed, please accept it so others will find it. $\endgroup$ – Brick Sep 19 '15 at 14:49
  • $\begingroup$ is it possible to ask question from a specific user on this forum ? $\endgroup$ – g g Sep 21 '15 at 4:13

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