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Explain DeBroglie wavelength to brainet

Anonymous Sun 11 Aug 17:54:59 2019 No.10880291 View Reply Original Report

Quoted By: >>10881016 >>10881126

If the wavelength is h/p, it follows that an object at rest has infinite wavelength. How is this possible?

Anonymous

Anonymous Sun 11 Aug 2019 17:59:21 No.10880299 Report

Quoted By:

There are no objects at rest.

Anonymous

Anonymous Sun 11 Aug 2019 18:03:36 No.10880305 Report

Quoted By: >>10880316

Intuitively, you'd expect the faster a particle is moving the greater its area of uncertainty is. At rest there would be exact certainty about its location. DeBroglie's equation seems the exact opposite of this.

Anonymous

Anonymous Sun 11 Aug 2019 18:09:25 No.10880316 Report

Quoted By: >>10881091

>>10880305
Simple explanation is in the uncertainty principle. If a particle has certain momentum (momentum variation is zero), her position can't be determined at all. It doesn't depend on the speed of the particle.

Anonymous

Anonymous Sun 11 Aug 2019 22:53:27 No.10881016 Report

Quoted By:

>>10880291
another way to think of it is in terms of a fourier transform. an object that is at rest, i.e. is a dirac delta FUNCTION (hehe) in position space, has a distribution in momentum space given by the fourier transform of the dirac delta, which is basically flat over all momentum space, meaning it has nonzero tails all the way to positive and negative infinity.

Anonymous

Anonymous Sun 11 Aug 2019 23:32:01 No.10881091 Report

Quoted By: >>10881215 >>10882953

>>10880316
Then the p in the matter wave equation doesn't represent momentum? It represents momentum uncertainty?

Anonymous

Anonymous Sun 11 Aug 2019 23:55:42 No.10881126 Report

Quoted By: >>10881182

>>10880291
https://www.youtube.com/watch?v=MBnnXbOM5S4

this is worth watching for a mathematical intution. combined with the fact that nothing can truly be at rest.

Anonymous

Anonymous Mon 12 Aug 2019 00:27:33 No.10881182 Report

Quoted By:

>>10881126
based video

Anonymous

Anonymous Mon 12 Aug 2019 00:44:34 No.10881215 Report

Quoted By: >>10882953

>>10881091
it does represent momentum. The uncertainty in p is only relevant at atomic/subatomic levels. After that any uncertainty is negligibly small and we don't have to worry about that, however at small levels there's always inherent uncertainty when talking about momentum in any case.

Anonymous

Anonymous Mon 12 Aug 2019 20:16:11 No.10882953 Report

Quoted By: >>10883436

>>10881091
They're saying the equation is about uncertainty in the variables.

>>10881215
This is wrong.

Anonymous

Anonymous Tue 13 Aug 2019 00:28:28 No.10883436 Report

Quoted By:

>>10882953
It seems then every representation of DeBroglie's equation is poorly written. I have never seen p written once anywhere in the context of momentum uncertainty.

Anonymous

Anonymous Tue 13 Aug 2019 00:33:45 No.10883451 Report

Quoted By:

Reminder that DeBroglie was a history major turned physicist. He literally guessed in his thesis. "Hey what if matter acts the same way as light" and jotted down a half baked formula that today we try to pretend makes sense. It literally doesn't. Everyone is too afraid to say its nonsense so I will say it, it doesn't make sense. He mentioned nothing about "uncertainty" in his original paper because he didn't understand what that mean in a quantum context. Truthfully I doubt he understood what a wave even was.

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