Quantum Mechanics

[antimatter]

I need a little help understanding how quanta and elementary particles tie in to quantum mechanics. I understand both of them, but it's the concept of quantum mechanics that gets me, it seems really random.

Can someone help explain the concept to me?

[swansont]

Everything is actually waves, and the waves — which represent things like the position/momentum/energy of the entity in question — must conform to boundary conditions. This excludes a great many solutions from being possible; the solutions that are left are discrete.

[antimatter]

Thanks for replying, but I'm not entirely sure what you mean by "everythng is actually waves", do you mean everything as in energy?

And how do waves represent those things?

sorry, it takes me a while to get these concepts sometimes

[Klaynos]

Everything, as in everything, photons, electrons, buckminster fulleries.... everything is a wave (and a particle)

 

The waves don't represent the things, they are the things!

[antimatter]

Okay, I'm starting to get the idea, but how does quanta play into this?

Photons aren't really a wave, are they?

I always assumed they were particles, except in space

[Klaynos]

Well you see the idea of wave and particle breaks down in quantum mechanics.

 

When we said everything is a wave, we would also have been correct in saying everything is a particle, depending how you measure something it will appear to be either one...

 

Photons are waves, and they are particles, as are electrons...

 

Quantisation comes into play because the energies (and other values) of these particles/waves only have fixed quantised values...

[antimatter]

What measurements make matter appear as a wave? particle?

[insane_alien]

well, you can diffract buckminster fullerene. that is wave behaviour.

 

you can also bounce it around. that is particle behaviour.

[Klaynos]

To add to IA...

 

The two classic examples are the young double slit experiment showing that photons (or lots of other stuff) are waves, and the photoelectric effect, showing that photons only come in discrete packets and are therefore particles.

[antimatter]

I've heard that term 'packets' used before, but I don't quite understand what you mean by it

[thedarkshade]

Two or more waves come together to form a wave packet!

 

Wave Packet

[antimatter]

http://en.wikipedia.org/wiki/Image:Wave_packet_%28no_dispersion%29.gif

 

So then what are the spaces in between the packets?

 

http://upload.wikimedia.org/wikipedia/commons/c/c1/Wave_packet_%28no_dispersion%29.gif

Image:Wave packet (no dispersion).gif

[OneSpace]

i am new here, i was following the thread with great intrest then wham, someone said bullshit and it all fell apart. please continue, what are the spaces inbetween?

[Klaynos]

In this case I don't think wave packets is what I meant by the term packet. I meant a lump of energy, a single discrete thing. Not a continuous wave...

 

The space in between, well it depends what medium you're moving through.

[antimatter]

oh Okay, so just like one of those big concentrations of waves?

[swansont]

oh Okay, so just like one of those big concentrations of waves?

 

Or a wave taking up only a small region, as opposed to a long wave-train.

 

Like this

[antimatter]

Thanks, that actually helps a lot!

[mustkara]

I am not sure any help for you but I would recommend the textbook

 

Introduction to Quantum Mechanics, 2nd Edition

 

that I use it when i was in university. This is a good quantum mechanice and should be easy to understand. Anyway, wish some help.

[HannonRJ]

Everything is actually waves, and the waves — which represent things like the position/momentum/energy of the entity in question — must conform to boundary conditions. This excludes a great many solutions from being possible; the solutions that are left are discrete.

 

Have you read how deBroglie derived his "wave-particle duality" equation?

Have you read Planck's article in which he expounded the "quantum"?

[swansont]

Have you read how deBroglie derived his "wave-particle duality" equation?

Have you read Planck's article in which he expounded the "quantum"?

 

Yes to the first, no to the second. Why, is that something you feel is important? Original papers are "works in progress." Concepts get refined and errors get corrected.

[insane_alien]

HannonRJ seems to think you cannot understand a subject unless you look at the older revisions of it where there were errors. as if the newer revisions did not contain everything the old version got right.