How do you explain the Heisenberg uncertainty principle?

[hamsa0]

So to determine the position of an object you can scatter light off of it. Fine. But then my textbook says you can't know the exact position of the object because of diffraction effects. We've covered the diffraction of light through narrow slits but I don't know why if you were scattering light off a ball or an electron or something that it would end up diffracted.

 

[phinds]

So to determine the position of an object you can scatter light off of it. Fine. But then my textbook says you can't know the exact position of the object because of diffraction effects. We've covered the diffraction of light through narrow slits but I don't know why if you were scattering light off a ball or an electron or something that it would end up diffracted.

The HUP has nothing to do with macro sized objects such as a billiard ball, it has to do with sub-atomic particle, which are a whole 'nother story.

 

[hamsa0]

K well since I haven't studied this so called whole 'nother story of diffraction by subatomic particles, I'll just have to believe everyone that there is in fact diffraction that causes uncertainty in the position. Thanks.

 

[phinds]

K well since I haven't studied this so called whole 'nother story of diffraction by subatomic particles, I'll just have to believe everyone that there is in fact diffraction that causes uncertainty in the position. Thanks.

I don't think diffraction has anything to do with what happens at the subatomic level in the sense of the uncertainty that the HUP describes, it is a matter of quantum uncertainty.

 

[tom.stoer]

One finds explanations relating the HUP to experiments quite frequently, but this is misleading. The HUP restricts the "existence" of sharp values, not only measurement accuracy in certain experiments. It is a rather simple mathematical excercise to derive the HUP for two non-commuting observables w/o every talking about experiments.

We had this discussion here a couple of times.

 

[San K]

So to determine the position of an object you can scatter light off of it. Fine. But then my textbook says you can't know the exact position of the object because of diffraction effects. We've covered the diffraction of light through narrow slits but I don't know why if you were scattering light off a ball or an electron or something that it would end up diffracted.

The HUP that randomness/uncertainty is a fundamental of existence. It has been observed for elementary particles such as photons, electrons (and some bigger atoms?) etc. yet.

 

[exponent137]

I don't think diffraction has anything to do with what happens at the subatomic level in the sense of the uncertainty that the HUP describes, it is a matter of quantum uncertainty.

I think that it have connection.
HUP is a consequence that Fourier distribution of location is distribution of momentum. (And oppositely) But, both momentum and location are sinusoidaly distributed. Similarly as diffraction...
But, you Hamsa describes Heisenberg microscope. It is good one for visualisation of HUP, but it is not the same thing. Heisenberg microscope contains hidden variables which are not existent according to tests of Bell equation.

 

[ZealScience]

In my opinion, diffraction causes uncertainty is because of degree of angular resolution. But it is pretty much on bigger object rather than particles decribed by quantum, like cells displayed by light microscopes. While talking about quantum, it deals with single photons. Photons with different wavelength act differently with electrons that causes different degree of uncertainty. Just my personal understanding.

 

[ZapperZ]

In my opinion, diffraction causes uncertainty is because of degree of angular resolution. But it is pretty much on bigger object rather than particles decribed by quantum, like cells displayed by light microscopes. While talking about quantum, it deals with single photons. Photons with different wavelength act differently with electrons that causes different degree of uncertainty. Just my personal understanding.

No. The HUP is inherent to ALL quantum particles, not just photons.

I've described previously how the single-slit diffraction is a clear manifestation of the HUP.

https://www.physicsforums.com/showthread.php?t=394171

Note that one can get the diffraction effects from photons, electrons, protons, neutrons, buckyballs, etc.

Zz.