# De Broglie Waves

1. Jan 4, 2005

### DB

Correct me where I'm wrong. De Broglie waves, are extremely small waves of matter equivilant to Planck's constant over the the particles momentum??

$$\frac{h}{p}$$

If so these would be extremely small waves. But if the formula is right, what exactly is the formula porportional too? Frequency, wavelenght???

Thanks

2. Jan 4, 2005

### quasar987

The formula is

$$\lambda = \frac{h}{p}$$

where lambda is the wavelenght of the wave. I think that was your question.

I would also like to point out, in case you did not know, that these "waves of matter" are not waves like those you see on the sea happening on the surface of matter. They are "abstract waves" whose nature were unknown at the time of their discovery by De Broglie. It was later found that the waves reprent the probability of finding the particle at a certain position in space: the higher the amplitude of the wave at that point, the higher the probability.

Another remark: the wavelenght is not necessarily small. As soon has you have a momentum that is about as small as h, then the wavelenght is big enough that you could see the waves if they were visible. For exemple, if p=h, the wavelenght is of 1 meter!

3. Jan 4, 2005

### DB

Thanks quasar, thats what I was looking for, the formula is equivalant to the wavelenght. And I guess I never thought that the smaller the momentum the bigger the wavelength, interesting stuff.

4. Jan 4, 2005

### derekmohammed

What is the largest matter wave that a person has observered? What would it look like? I mean in something very large with a large wave... Thanks

5. Jan 5, 2005

### Kea

How about a low E neutrino at one of the South Pole detectors?

6. Jan 10, 2005

### jet10

destructive interference

What happens if you have two similar wave particles interfere destructively: would the particles disappear? probably not... but what happens?

7. Jan 10, 2005

### kirovman

The probabity of finding the particles there would be zero.

8. Jan 12, 2005

### jet10

where does the energy or the particle go to, if the two waves completely eliminate each other?

9. Jan 12, 2005

### marlon

For example if an electron and a positron interact they will annihilate each other. This means that the energy coming from these two particles is converted into other particles like a photon pair for example. Basically what will happen is conversion into other particles. The rules that need to be respected are called conservation laws. for example an electron and a positron have opposite charge. This implies that the resulting photons may not exhibit charge due to this conservationlaw. Ofcourse photons DO NOT have charge so tha's ok. Also energy needs to be conserved,...

regards
marlon

10. Jan 12, 2005

### dextercioby

...4-momentum actually.Lepton number,spin,isospin,baryon number,etc...

Daniel.

PS.U know that Gauss and Riemann had nothing to do with absolute differential calculus... So let's not put them together with Ricci and Christoffel vs.quaternions of Mr.Hamilton.

11. Jan 12, 2005

### marlon

i hope this is meant to be a joke...

marlon

12. Jan 12, 2005

### dextercioby

Nope,tensor calculus was developed after the works of Gauss and Riemann. You may remember who put the names "tensor" into physics... What about "curl"??What about "gradien"??""Nabla"??"Divergence"??"Covariant differential"?Christoffel symbols??(Nope,that's too simple... :tongue2: )

History,Marlon...

Daniel.

13. Jan 12, 2005

### marlon

It sure is, dexter....

marlon

14. Jan 12, 2005

### dextercioby

Nope,pioneer was Augustin Cauchy.He used the notion "tensor" when speaking about TENSIONS (quite similar to "tensor",right ?? ) in fluids.

Tensor calculus means calculus with tensors...And it doesn't concern K.F. Gauss and B.Riemann.

BTW,they pioneered differential geometry.Tensor calculus was merged with differential geometry in the 1900-s by Weyl and Elie Cartan...

Daniel.

EDIT:Maybe we should allow a mathematician have his say...

EDIT2:Anyway,we've diverted this thread from de Broglie's waves to history of mathematics... :tongue2:

Last edited: Jan 12, 2005