Weird AS Physics wave motion question

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TheKevinFang
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For question 7b II

Why is the motion of the particle on the transverse wave down not up, and why isn't the motion of the particle on the longitudinal wave left not right?

Also bonus question :

Why is the electron diffraction more accurate than distance of closest approach? Apparently it is because it doesn't interact the with strong nuclear force, why would that affect the accuracy?
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Eimmanuel
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(Original post by TheKevinFang)
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For question 7b II

Why is the motion of the particle on the transverse wave down not up, and why isn't the motion of the particle on the longitudinal wave left not right?
Not really sure what you are asking.
For the transverse wave:

Name:  transverse_wave01.JPG
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Say the pink curve is modelling the transverse wave profile at a particular instant. The red curve is showing the wave profile at a little time later.
The black dot is representing the point P. It is seen that the point P moves up when the wave travels to the right a little time later. So the particle should be moving up.


The next picture (seems to be an attachment) is modelling the longitudinal wave. Point Q seems to be the center of rarefaction which is particle 8 in the top graph.
The top graph is the wave profile when t is zero. The bottom graph is the wave profile when t is T/8. The blue curve is the displacement versus position graph of the longitudinal wave.
You can see that particle 8 moves to the left when t is T/8. So the particle should be moving left.

Your bonus question is more weird than the wave question. Cannot figure out what you are trying to ask. It seems that there is some info before this question. You ask why is electron diffraction more accurate than distance of closest approach, more accurate of what?
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TheKevinFang
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(Original post by Eimmanuel)
Not really sure what you are asking.
For the transverse wave:

Name:  transverse_wave01.JPG
Views: 182
Size:  39.9 KB

Say the pink curve is modelling the transverse wave profile at a particular instant. The red curve is showing the wave profile at a little time later.
The black dot is representing the point P. It is seen that the point P moves up when the wave travels to the right a little time later. So the particle should be moving up.


The next picture (seems to be an attachment) is modelling the longitudinal wave. Point Q seems to be the center of rarefaction which is particle 8 in the top graph.
The top graph is the wave profile when t is zero. The bottom graph is the wave profile when t is T/8. The blue curve is the displacement versus position graph of the longitudinal wave.
You can see that particle 8 moves to the left when t is T/8. So the particle should be moving left.

Your bonus question is more weird than the wave question. Cannot figure out what you are trying to ask. It seems that there is some info before this question. You ask why is electron diffraction more accurate than distance of closest approach, more accurate of what?
Hi, I meant why is electron diffraction more accurate for approximating nuclear radius, I'm still unsure.

I understand the transverse wave particle movement now but the graph for the longitudinal wave is really confusing, I'm not sure why at t/8 the particles look like that. Could you explain it more simply if possible?

Thank you!

Edit: I understand the longitudinal wave now but it's still somewhat confusing
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Eimmanuel
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(Original post by TheKevinFang)
Hi, I meant why is electron diffraction more accurate for approximating nuclear radius, I'm still unsure.

I understand the transverse wave particle movement now but the graph for the longitudinal wave is really confusing, I'm not sure why at t/8 the particles look like that. Could you explain it more simply if possible?

Thank you!

Edit: I understand the longitudinal wave now but it's still somewhat confusing
I agree that my posting may be confusing and to really appreciate the motion of the particle in the longitudinal wave is not an easy in the first look. I can take about 45 min to tutor some of my students to draw the motion of the particles.

You can still ask questions what is confusing you.

I think electron diffraction is more accurate in determining the nuclear radius is because alpha particle would experience electrostatic repulsion but electron would not have such issue. So electron can get closer to the nucleus.
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Adam_1999
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The answer as to why electron diffraction is more accurate is because the alpha particle never reaches the nucleus; its point of closest approach is a small, but considerable distance away.
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Donovannoble
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Actually the point Q isn't moving at all, as it is at the centre of rarefaction and the points on either side will move towards it, although the profile of the wave will move this point will not. I believe the exam paper is wrong.
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Eimmanuel
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(Original post by Donovannoble)
Actually the point Q isn't moving at all, as it is at the centre of rarefaction and the points on either side will move towards it, although the profile of the wave will move this point will not. I believe the exam paper is wrong.
There is nothing with the question. The question asks how would the point Q move in the next instant.
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