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# what wil happen if two rays of light hit each other directly? Answered

will they neutralized each other? will the bonce off each other? or will they just go through each other?

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## 6 Replies

rickharris (author)2009-06-29

If you think of light as waves at a specific frequency for each colour then the light waves may interact - look up diffraction http://encyclopedia.farlex.com/Defraction which also applies to light.

or

http://en.wikipedia.org/wiki/Diffraction

the people at http://howwhatwhy.com/forum/index.php will provide more detail if you require it.

kelseymh (author)2009-06-30

Diffraction is the interaction of light waves with opaque edges, not light-on-light scattering. As both Kiteman and I have noted, waves do interfere with each other, so if you place a detector at the location whether they are crossing, you can see those interference (not diffraction) effects. However, if you place a detector at a different location, "after" the interference region, then you will see clearly that the waves passed through each other without making any persistent changes.

kelseymh (author)2009-06-29

Most of the time, nothing at all. The amplitudes for the electric and magnetic fields in a classical light wave are so small that the possible interactions are immeasurable. As Kiteman said, however, if you make an observation at the point where the two beams hit or cross, then you can see interference effects between the waves.

In quantum electrodynamics, there is no direct interaction between two photons. However, it is possible for a virtual electron-positron pair to induce a secondary interaction (for the technically minded, this is an O(alpha4) amplitude loop interaction). The probability is so low, however, that you need really intense beams (gigawatt lasers aren't even strong enough), and very sensitive detectors to see any effect.

steveastrouk (author)2009-06-30

I think the OP is imagining that they have the beams in full anti-phase, and expecting to see the beams cancel to nothing. From your explanation this clearly doesn't happen !

Emsaid (author)2009-06-29

They will go right through each other

Kiteman (author)2009-06-29

They will pass through each other, but at the point where they share the same space there will be either contstructive interference or destructive interference (google that).