Can Coherent Light Waves Interfere with Each Other?

In summary, If two beams of light, in a vacuum, are projected towards each other will the beams be reflected ? This is a more well-defined question. The answer is, no, at least at the everyday level. In classical wave picture, when two light beam overlaps, they produce a superposition effect (the same one that produces the interference effect). So they simply "add" according to the phase of the light wave. However, if you include quantum electrodynamics (QED) this can result in a scattering of photons.
  • #1
Dipto
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If two beams of light, in a vacuum, are projected towards each other will the beams be reflected ? If not what will happen ?
 
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  • #2
No there will be no reflection , there will be wave interference instead. In short there will be a new beam that will be brighter than any of the two but what i just said is probably an oversimplification , check http://en.wikipedia.org/wiki/Interference_(wave_propagation ) especially the section about optical interference.
 
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  • #3
Dipto said:
If two beams of light, in a vacuum, are projected towards each other will the beams be reflected ? If not what will happen ?

So, let me first start by saying that this is a good opportunity for you to learn a little bit about the correct "phrase" to use, so that your question will come out the way you intended to ask, or it'll come out more accurately based on what we know about physics.

When two things collide or interact, one seldom use the term "reflected", because reflection is a well-defined observation. The more accurate term to be used here is "scatter". So it is my guess that you're asking of two light beam scatter off each other. This is a more well-defined question.

The answer is, no, at least at the everyday level. In classical wave picture, when two light beam overlaps, they produce a superposition effect (the same one that produces the interference effect). So they simply "add" according to the phase of the light wave.

The situation when you include quantum electrodynamics (QED) isn't that easy anymore. One can have photon-photon collisions, but this is extremely rare, often requires high energy photos (gammas), and it doesn't always just result in a scattering of these photons, but also the creation of other particles. This is not something you normally encounter everyday.

So if you want just one take-home answer, it would be "No."

Zz.
 
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  • #4
ZapperZ said:
So, let me first start by saying that this is a good opportunity for you to learn a little bit about the correct "phrase" to use, so that your question will come out the way you intended to ask, or it'll come out more accurately based on what we know about physics.

When two things collide or interact, one seldom use the term "reflected", because reflection is a well-defined observation. The more accurate term to be used here is "scatter". So it is my guess that you're asking of two light beam scatter off each other. This is a more well-defined question.

The answer is, no, at least at the everyday level. In classical wave picture, when two light beam overlaps, they produce a superposition effect (the same one that produces the interference effect). So they simply "add" according to the phase of the light wave.

The situation when you include quantum electrodynamics (QED) isn't that easy anymore. One can have photon-photon collisions, but this is extremely rare, often requires high energy photos (gammas), and it doesn't always just result in a scattering of these photons, but also the creation of other particles. This is not something you normally encounter everyday.

So if you want just one take-home answer, it would be "No."

Zz.
thanks
 
  • #5
As an addition to ZapperZ's answer, this QED process is called Delbruck scattering . Photon's spontaneously create virtual electron-positron pairs which interact.
This is actually one of the most prominent mechanisms of gamma ray attenuation in high energy astrophysics.
 
  • #6
Delta² said:
No there will be no reflection , there will be wave interference instead. In short there will be a new beam that will be brighter than any of the two but what i just said is probably an oversimplification , check http://en.wikipedia.org/wiki/Interference_(wave_propagation ) especially the section about optical interference.
Not true, in general. The interfering beam needs to be coherent with the beam that you want to affect. That more or less demands that both beams come from the same source (or from two synchronised lasers). The resulting interference pattern will not consist of 'a beam' because you cannot get the two beams, of finite width, to coincide so that the path differences are the same across a whole plane. You will produce a set of fringes or a standing wave pattern and this even happens if the two beams are launched along the ends of an optical fibre.
(NB. The total power is not altered so input power is 'redistributed' but not reduced or enhanced)
 
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FAQ: Can Coherent Light Waves Interfere with Each Other?

1. Can light actually reflect light?

Yes, light can reflect light. Reflection is the process in which light bounces off a surface and changes direction. This phenomenon is what allows us to see objects around us.

2. How does light reflect off of different surfaces?

The way light reflects off a surface depends on the material and texture of the surface. Smooth and polished surfaces, like mirrors, reflect light in a regular and predictable way, creating a clear image. Rough and uneven surfaces reflect light in different directions, causing objects to appear blurry or distorted.

3. Does all light reflect at the same angle?

No, the angle of reflection depends on the angle at which the light hits the surface. According to the law of reflection, the angle of incidence (incoming light) is equal to the angle of reflection (reflected light).

4. Can light reflect off of transparent materials?

Yes, light can reflect off of transparent materials like glass and water. This is because even though the material is transparent, it still has a surface that can reflect light.

5. Can light reflect multiple times?

Yes, light can reflect multiple times, creating a series of reflections known as a "multiple reflection." This can occur in mirrors, where light reflects off the first surface and then reflects off the second surface at a different angle. This is also the principle behind "infinity mirrors," where multiple reflections create the illusion of an infinite number of reflections.

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