Heisenberg's uncertainty principle

1. Jan 10, 2009

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?

2. Jan 10, 2009

malawi_glenn

3. Jan 10, 2009

DrChinese

A great example is electron spin. An electron has 3 non-commuting spin components: x, y and z. Knowledge of any one 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.

4. Jan 11, 2009

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!

5. Jan 11, 2009

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.

6. Jan 11, 2009

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?

7. Jan 11, 2009

malawi_glenn

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

So it is no big deal.