Product of Interference

[Mukilab]

Hello everyone,

 

This forum has finally helped me to answer nearly all my questions, which even my teachers could not help me with.

 

One question remains unanswered to me though.

 

I was recently told of the experiment to prove the quantum mechanics theory of atoms being everywhere at the same time, literally.

 

Since I don't know the name I'll try to describe it. You have a material with two gaps near the middle, at the exact same distance from the middle as each other. Particles, whether photons or something else it does not matter are fired at one of the holes and as it comes out the other side an interference is causes (I'm unsure of whether this technical term is correct). This interference can only be caused by two atoms (hitting?) each other, proving that atoms can be in several places at the same time.

 

But the question is. What is the product of this interference? Energy? Mass can't be destroyed without trace and if the waves are at the highest and lowest points than all you'll get is a straight line...

 

 

On another, separate note; if an atom can be in one place at any given time than will it have the same probability to be in another place? How can we calculate this probability but never observe two positions at the same time?

 

I've heard several people talking about the existence of parallel universes and their argument of never seeing these universes (assuming that quantum mechanics can be enlarged, which it can't due to gravity) is that you can't observe an atom in two places at the same time.

 

So let's say we observed that parallel universe than ours would not exist to us anymore? Does anyone have an example, simplifying this?

 

~Cyfer/Muki

 

 

EDIT::: sorry the title was meant to be: Product of Interference

Edited November 15, 2009 by Mukilab

[swansont]

It's called Young's double-slit experiment. Classically speaking, when a wave goes through, the two slits act as point sources, and at certain positions you will get constructive interference (the waves add) and at others, destructive interference (the waves cancel)

 

But you still see this effect with photons when only one "particle" is in the apparatus at a time, meaning the photon interferes with itself. In one view, the particle is in two places at one time. However, I am of the opinion that this "view" is just an attempt to explain quantum mechanics with classical notions — in this case holding on to notions like well-defined positions and trajectories — and that presents a problem as you try and make this model cover more physics.

 

Light is a wave, but the energy is quantized. It is localized when it interacts, and that tempts us to think of it as a particle. But thinking of it as a particle at any time other than the interaction can lead you astray. Since light is a wave, you have to think of it as existing over a large area or volume, rather than a single point. This is true of things with mass, as well. Electrons are "smeared out," though when you try and interact with them (in some ways, at least), they are localized to an arbitrarily small volume.

 

 

When you have interference, the energy will always show up somewhere, i.e. there will always be a region of constructive interference (a signal) if there is a region of destructive interference (no signal).

 

EDIT::: sorry the title was meant to be: Product of Interference

Fixed

[Mukilab]

It's called Young's double-slit experiment. Classically speaking, when a wave goes through, the two slits act as point sources, and at certain positions you will get constructive interference (the waves add) and at others, destructive interference (the waves cancel)

 

By waves adding, do you mean they heighten in intensity? Usually I would say age does not matter but for once I'm lost, I'm 13. Please could you explain these either more in depth or simplified?

 

 

But you still see this effect with photons when only one "particle" is in the apparatus at a time, meaning the photon interferes with itself. In one view, the particle is in two places at one time. However, I am of the opinion that this "view" is just an attempt to explain quantum mechanics with classical notions — in this case holding on to notions like well-defined positions and trajectories — and that presents a problem as you try and make this model cover more physics.

 

This is what I meant, that this one photon must be in two places in the same time.

But, how is it possible that it causes interference? I understand it must be in two places for it to pass through both slits, but at the point of interference it must be in a single place, so why cause interference? Before there might be interference from it being in two different places but at this point, it HAS to be in one place.

 

Sorry this paragraph isn't well defined, I don't really know how to voice my current thoughts.

 

Could you explain the problems this experiment encounters?

 

Light is a wave, but the energy is quantized. It is localized when it interacts, and that tempts us to think of it as a particle. But thinking of it as a particle at any time other than the interaction can lead you astray. Since light is a wave, you have to think of it as existing over a large area or volume, rather than a single point. This is true of things with mass, as well. Electrons are "smeared out," though when you try and interact with them (in some ways, at least), they are localized to an arbitrarily small volume.

 

What do you mean by quantized and localized? I can think of various definitions but I'm not sure whether they are correct.

Waves cover a large area? I've been severely mislead, I, to this point, believe that all waves are high-stream gamma-like directed waves. Those the area affected by the wave depend on (a rubbish example, sorry) the volume of sound? What I mean is, if, on a graph the trough and such is further from the middle line, does this affect the area it is passed through?

 

Please explain the electrons part, I do not have an idea at all of what you mean there, apart from the 'when you try and interact with them'. By this do you mean, try to observe them?

 

When you have interference, the energy will always show up somewhere, i.e. there will always be a region of constructive interference (a signal) if there is a region of destructive interference (no signal).

 

 

Fixed

 

If interference is done in a vacuum, how can there be a region of destructive interference?

 

 

Thanks for answering all my questions so fast. Many thanks.

 

~Cyfer/Mukilab

[swansont]

Quantum physics is pretty advanced stuff. I applaud your interest and effort, but there's a lot of ground to cover and you might be trying to absorb too much at once.

 

Constructive interference is higher intensity, destructive is lower (i.e. zero), and this is a behavior of waves. So even though we have a single quantum of EM energy, i.e. a photon, passing though the slits, it goes through both slits and interferes with itself. If you repeated this many times, you would see the standard interference pattern emerge. It doesn't matter if this is done in a vacuum, because light has no problem traveling through a vacuum.

 

"Being in two places at once" is a notion that arises by trying to think of the photon as a particle, when it's a wave.

[Mukilab]

Quantum physics is pretty advanced stuff. I applaud your interest and effort, but there's a lot of ground to cover and you might be trying to absorb too much at once.

 

Constructive interference is higher intensity, destructive is lower (i.e. zero), and this is a behavior of waves. So even though we have a single quantum of EM energy, i.e. a photon, passing though the slits, it goes through both slits and interferes with itself. If you repeated this many times, you would see the standard interference pattern emerge. It doesn't matter if this is done in a vacuum, because light has no problem traveling through a vacuum.

 

"Being in two places at once" is a notion that arises by trying to think of the photon as a particle, when it's a wave.

 

Finally my teacher agreed to meet up with me!

 

Explained a lot of things, posed more questions and told me to research various things such as Planck's law and Schrodinger's equation (I knew about the cat, but never that it was related to this).

 

I fully understand interference and I've had my questions on a vacuum answered.

 

I was only disappointed in myself since I couldn't ask several questions due to me being unable to think of a way to phrase them. And quite stupidly, near the end I messed up creating mass the subject in Einstein's famous equation... I was very tired...

 

 

Before I pose more questions do you know where I could find a place for questions in Chemistry up to A-Level standard? I've been practicing with my school as I've been selected for a competition but I've run out of sites!

 

This is probably in the wrong section, I apologize.