Naked Science Forum
Non Life Sciences => Physics, Astronomy & Cosmology => Topic started by: Lewis Thomson on 22/02/2022 12:16:17
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Alacyn has presented this question to The Naked Scientists.
"While looking at the Chladni Plate experiments, I understand studies by Hans Jenny and other scientist show that chaos occurs when any matter is rearranging itself into a new form based on the new frequency. My question is does the sand/salt permanently absorb that frequency? It seems implied but I can’t find anything that specifically states that. Would the resonate frequency be absorbed and permanently fixed if say you bottled it up. If so, is there a way to test this?"
What do you think? Leave your answers in the comments below...
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Frequency isn't something that can be absorbed (or bottled). Whatever the frequency, the friction between moving grains of sand/salt will dissipate mechanical energy as heat (that's how gravel traps (https://goo.gl/maps/8GHQqnzwaqMewPDf9) at the side of roads work).
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The patterns formed on Chladni plates are a result of the properties of the plates themselves, and has nothing to do with the sand/salt/sugar/dust/etc. placed on top for visualization purposes. The grains that are arranged into the pattern are "agnostic" of why they are in the particular place that they are in.
The plate vibrates in such a way that parts of the plate have significant displacement, and other parts hardly move at all (the "nodes"). Grains that happen to be on parts of the plate that are moving get tossed up and land on another part of the plate, while grains that happen to be on the nodes where the plate is hardly moving get to stay put. This means that after a brief period, almost all of the grains end up on the parts of the plate that are hardly moving. The pattern that the nodes make is a function of the frequency of the vibration and the size/shape of the plate.
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My question is does the sand/salt permanently absorb that frequency?
No.
It doesn't do anything interesting apart from get kicked off the bits of plate that are vibrating.
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The patterns formed on Chladni plates are a result of the properties of the plates themselves, and has nothing to do with the sand/salt/sugar/dust/etc. placed on top for visualization purposes. ..... The pattern that the nodes make is a function of the frequency of the vibration and the size/shape of the plate.
Fully agree, acid test is that the pattern changes with frequency, so there is no memory effect.
PS I use tea leaves, but don’t read anything into that ;D
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Those Chladni Plate experiments are quite interesting.
https://americanhistory.si.edu/science/chladni.htm
http://www.vhf-interservice.com/projects/weather/howItWorks_gb.html
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Hi.
The patterns formed on Chladni plates are a result of the properties of the plates themselves, and has nothing to do with the sand/salt/sugar/dust/etc. placed on top for visualization purposes.
Almost entirely true.
If you get silly and start using extremely fine grained powders you sometimes do get alternative patterns forming. The main explanation for this seems to be that the air movement above the plate starts to become important for moving the particles around so that the particles don't get deposited at a node for the plate but instead they get deposited where air currents take them.
I'm going to guess that there is some critical value of the surface area to mass ratio (for the ultra-fine particles) so that the cross-section of the particles exposed to the air currents for the time they are above the plate becomes more important than the brief period of contact they have with the plate.
See this video by Sixty Symbols at time index approx 2:45 where they add an exceptionally fine powder.
WARNING: Nasty sounds when that plate vibrates, turn your speaker volume down now.
Best Wishes.
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Hi.
The patterns formed on Chladni plates are a result of the properties of the plates themselves, and has nothing to do with the sand/salt/sugar/dust/etc. placed on top for visualization purposes.
Almost entirely true.
If you get silly and start using extremely fine grained powders you sometimes do get alternative patterns forming.
Chladni also saw this effect on very fine particles, Faraday thought it was due to air currents carrying the particles around.
Interestingly, you get an effect in water where even large particles move to the antinodes. It’s been suggested that the drag force of the water makes it harder for them to lift off the surface and they are driven horizontally by surface waves on the plate and gravity. In order to see why it happens you have to average the horizontal forces over a complete cycle, otherwise it appears counterintuitive.
However, the supposition by the OP of a memory effect is still incorrect ;D
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Hi.
Thanks for the info @Colin2B .
I was wondering if the larger particles would move to the anti-nodes in denser air, for example if the equipment was moved to a hyper-baric chamber. Doing the experiment in a dense fluid like liquid water seems to be much the same idea. Presumably the ultra-fine particles should move to the nodes if you perform the experiment in a vaccum.
(i.d.k. I've not seen it done).
Best Wishes.