# I What is this effect

Tags:
1. Apr 22, 2017

### TBert

A friend of mine showed me a diagram like this:

I think they said it was describing the probability of finding a charged particle in a certain place when traveling over a voltage. They said that if the particle doesn't have enough energy to make it across then it gets stuck at the beginning of the voltage. I'm wondering if anyone can identify what effect/physics law this is a give me a better description of how it works

2. Apr 22, 2017

### bhobba

Look up quantum tunneling.

Thanks
Bill

3. Apr 23, 2017

### TBert

They said it was different from quantum tunneling though because there wasn't a barrier the was being passed

4. Apr 23, 2017

### bhobba

Its a potential barrier. If it has enough energy it can jump the barrier. That's the funny thing about QM because it doesn't have an energy until actually measured it can be found outside a barrier that doesn't require an infinite energy to jump.

The QM particle in a box might be slightly more instructive for you. Have a look at the infinite barrier box first then the case of a finite wall:
http://hyperphysics.phy-astr.gsu.edu/hbase/quantum/pbox.html

Thanks
Bill

5. Apr 23, 2017

### TBert

Are you sure it is a potential barrier? They seemed very sure about the fact that it wasn't a barrier or quantum tunneling. They made it seem like it was a force to the electricity.

6. Apr 23, 2017

### Staff: Mentor

That's what a potential barrier is.
People use the word "tunnelling" more or less narrowly to describe the phenomena that are observed when an incident wave encounters a change in potential, but the physics you're looking for is Schrodinger's equation for a one-dimensional potential.... But I don't think your diagram corresponds to any correct solution of that equation.

7. Apr 23, 2017

### Staff: Mentor

Did he tell you what the horizontal and vertical axes of the diagram represent? If not, it's really hard to know what the diagram is supposed to be telling you.

8. Apr 23, 2017

### Roger Dodger

Looks like someone took a sloppy representation of the first excited state of a particle in a well and elevated it above the well. I certainly wouldn't put any stock in this image.

9. Apr 23, 2017

### TBert

For the curvy line on top the vertical axes is the amount of particle in the position and the horizontal axes is the position (like in one dimension). For the bottom line the vertical and horizontal axes show where the charge is.

10. Apr 23, 2017

### Staff: Mentor

What does this mean? "Amount of particle" is not a physical quantity.

Are you sure?