Diffraction

[swansont]

 

Which wave equation? How are bounderies applied in this equation?

 

The only wave equation that works for EM waves: the one from Maxwell's equations. The boundary conditions are given in the link I provided.

[DParlevliet]

It stems from Huygens principle

http://www.math.ubc.ca/~cass/courses/m309-03a/m309-projects/krzak/

 

This is the only link I found. There are no Maxwell's equations and no bounderies are filled in.

 

But it mentions (as was mentioned in the Huygens principle): "When the light encounters the slit, the pattern of the resulting wave can be calculated by treating each point in the aperature as a point source from which new waves spread out"

 

So diffraction is based on every point in the slit radiating as a point source. Then the question remains, what does radiate? Perhaps QM say: we don't know. That is good option. But a more logical conclusion would be that it is "something". Certainly not a classical medium, but stil something.

[swansont]

This is the only link I found. There are no Maxwell's equations and no bounderies are filled in.

The sinusoid, which is what they use, is a solution to the wave equation. They apply that to the slit to determine the diffraction.

 

But it mentions (as was mentioned in the Huygens principle): "When the light encounters the slit, the pattern of the resulting wave can be calculated by treating each point in the aperature as a point source from which new waves spread out"

 

So diffraction is based on every point in the slit radiating as a point source. Then the question remains, what does radiate? Perhaps QM say: we don't know. That is good option. But a more logical conclusion would be that it is "something". Certainly not a classical medium, but stil something.

"What radiates?" is a very different question from "how do you explain diffraction?"

[DParlevliet]

The sinusoid, which is what they use, is a solution to the wave equation. They apply that to the slit to determine the diffraction.

 

"What radiates?" is a very different question from "how do you explain diffraction?"

 

Diffraction is based on the assumption of treating each point as a source of new waves. Without that, there is no diffraction, also not with a EM sinusoid.

 

That is how diffraction is explained. Part of the question is how the wave is causing those points to be a new wave. After this discussion I suppose that QM does not know, or better does not try to know. From a Copenhagen point of view that a is good answer.

 

 

[swansont]

Diffraction is based on the assumption of treating each point as a source of new waves. Without that, there is no diffraction, also not with a EM sinusoid.

 

That is how diffraction is explained. Part of the question is how the wave is causing those points to be a new wave. After this discussion I suppose that QM does not know, or better does not try to know. From a Copenhagen point of view that a is good answer.

"Causing" is not part of the framework. There is no claim that this is physically happening. This is physics, and all physics is saying is that waves can be modeled this way.

[Strange]

That is how diffraction is explained.

That is how diffraction is modelled.

 

After this discussion I suppose that QM does not know, or better does not try to know.

QM uses a completely different model. Which, nicely, comes up with the same answers.

[DParlevliet]

That is how diffraction is modelled.

QM uses a completely different model. Which, nicely, comes up with the same answers.

 

And that is?

[Strange]

And that is?

 

QED. (Sorry, I thought that had been referenced here before.)

[Mike Smith Cosmos]

 

It would seem to me this subject of what radiates in what medium is a constant concern to many . Times have moved on. The old ideas of nothing or something maybe does not necessary apply any more.

Today 10 trillion neutrinos can pass through our hand in one second without us noticing. Goodness knows , it takes a light year of lead for one neutrino to react with ordinary matter we are told. Perhaps we in our macro world is so spaced out in distance, that all this other miniature stuff is going about a different business!

If you are a photon working at plank lengths or there abouts, perhaps all this micro miniature stuff is important to its operation " not the medium that has been discarded but a sort of new medium " to us we do not even notice it ,any more than we do neutrinos.

 

I hear the shot gun being loaded !

[DParlevliet]

QED. (Sorry, I thought that had been referenced here before.)

 

If you mean Feynman: the calculation is different but the principle is the same: every point in space radiates spherical.

 

If we use Huygens for diffraction, then it includes that the wave is propagated by every point in space which radiate spherical. That is the real Huygens principle. Later on Fresnel used it for explaning diffraction.