A question about the double-slit experiment

[r731]

In the diagrams illustrating the double-slit experiment, I see waves extending longitudinally towards the the metal sheet. What if the waves were modeled differently so that they extended transversely in the diagrams? I've got the feeling that this can say something different.

 

[Vanadium 50]

What if the waves were modeled differently so that they extended transversely in the diagrams?

What do you mean by this?

 

[Nugatory]

What if the waves were modeled differently so that they extended transversely in the diagrams?

The best pictures of an idealized double-slit experiment show the waves emerging from the slits and spreading in all directions, something like https://www.ck12.org/book/ck-12-physics-concepts-intermediate/r8/section/15.1/

 

[r731]

What do you mean by this?

I mean that a beam is modeled as a wave crossing the metal sheet orthogonaly.

 

[Ibix]

I mean that a beam is modeled as a wave crossing the metal sheet orthogonaly.

Are you asking: if the incident radiation is polarised, does the angle between the polarisation direction and the slits affect the diffraction pattern? No it doesn't.

 

[Vanadium 50]

I mean that a beam is modeled as a wave crossing the metal sheet orthogonaly.

You mean the beam is perpendicular to the sheet? This is the situation usually discussed in texts.

 

[jbriggs444]

I think that the [very confused] idea is that the picture shows the wave front extending at right angles to the direction of propagation.

In a transverse wave, the disturbance is at right angles to the propagation direction. For instance, the up-and-down motion of water when a wave moves past. Or the EM field direction for a radio wave.

In a longitudinal wave, the disturbance is in the propagation direction. For instance, the forward and back motion of the air molecules when a sound wave moves past.

But the drawings for the double slit experiment have nothing to do with this. They are drawing the wave front. The wave front is in the same place regardless of the nature of the disturbance that is being propagated. Waves always propagate at right angles to the wave front. It does not matter whether it is a transverse or longitudinal.

 

[sophiecentaur]

Are you asking: if the incident radiation is polarised, does the angle between the polarisation direction and the slits affect the diffraction pattern? No it doesn't.

One mechanism that can explain how the radiation gets out of the slit then you could treat it as an RF problem. Imagine a finite depth of slit and currents flowing in and out of the sides of the slit and across the face of the plate, near the slit. A simple analysis assumes that all the components that the diffraction integral uses are all parallel , in a particular direction. This is OK when not far from the axis but near the plane of the metal screen, it can't really be assumed and the depth of the slit sides become relevant - and also the material that the screen is made of.

The further off the axis, the lower the level of the flux, if you use a simple calculation but the more significant are the other, non-ideal, factors. These other factors will produce infinitessimal field contributions that are not actually parallel so you can't add them up simply.

It's just another example of end effects and edge effects that occur everywhere. It all depends on how accurate you want your answer.