Heisenberg's uncertainty principle

[filippo]

As the above principle says, momentum and position can't be known both at the same time (Δx Δp ≥ h/4π); I am trying to find another example and I was thinking of energy and time following Einstein's box example...does anyone have an idea on whether it'c ocrrect or just another example?

 

[malawi_glenn]

http://en.wikipedia.org/wiki/Uncertainty_principle

 

[DrChinese]

A great example is electron spin. An electron has 3 non-commuting spin components: x, y and z. Knowledge of anyone means there is complete uncertainty in the other 2. You will often find it easier to appreciate the HUP if you consider spin rather than p or q. Ditto for photons.

 

[karkas]

Just to recover that thread and not create a new one, can you please answer my question here?

What's the difference between the Δx * Δp = h/2pi and Δx * Δp = h/4pi equations I find everywhere on the internet and textbooks?

My High School book has the first one, yet I seem to meet the other one more frequently.

Thanks!

 

[malawi_glenn]

depends on conventions in the derivations I guess. I can derive so one get Δx * Δp > h-bar/2

Please note that sometimes you have h and sometimes h-bar.

 

[karkas]

Yea so far I've seen these candidates for the place after >=

1)h
2)h-bar
3)h/2pi
4)h-bar/2

Interesting, so there isn't any standard formula you can use in any occasion? Or can you use any of these approximately?

 

[malawi_glenn]

well, you don't "use" HUP while solving REAL things ;-)

So it is no big deal.