If electrons are waves, what causes them to change direction?

[LSMOG]

If electrons are waves, what causes them to change direction and move up and down?

 

[lekh2003]

What exactly do you mean by move up and down? As in the electron-wave moving up and down conventionally?

 

[LSMOG]

What exactly do you mean by move up and down? As in the electron-wave moving up and down conventionally?

If you move along a sine graph, you move up and down because it is a wave

 

[weirdoguy]

So? What it has to do with electron? Electron is not a wave, nor classical particle. It's quantum particle, and those don't act the way you think they do. Sometimes they act wave-like but that does not make them (classical) waves.

 

[jtbell]

If you move along a sine graph, you move up and down because it is a wave

Electrons (or other particles for that matter) don't do that. The QM wave function doesn't represent motion in space like water molecules in a water wave or air molecules in a sound wave.

 

[ZapperZ]

If you move along a sine graph, you move up and down because it is a wave

But that is ONLY if the sine graph is drawn in real space!

The "wave" that you are referring to is described by quantum mechanics, and this wave resides in what is known as "configuration space". Furthermore, this is not a wave as in water waves. This is a "probability wave" (if we use the Copenhagen Interpretation). This wave describes the properties of ALL the observables related to the electrons: position, momentum, spin, charge, etc...etc., meaning it contains all the properties of the electron that can be measured.

So this is a good point to give you a basic lesson to everyone who does not have a formal introduction to physics, and QM in particular. Never, EVER simply focus on the "NAME" or label being given to something in physics, and then think that the pedestrian, everyday usage of that label or word means the same as it does in physics. This example of the misunderstanding of the word "wave" is one clear scenario.

Zz.

 

[LSMOG]

Oh thanks, maybe it is because I don't understand in what sense is an electron a wave. PLEASE give me an idea because all I did in physics is calculating deBroglie wave length without understanding in what sense is an electron a wave

 

[A. Neumaier]

I don't understand in what sense is an electron a wave. PLEASE give me an idea

Any superposition of waves in different directions is again a wave in the sense of quantum mechanics! Thus in general, a wave function describing an electron has no distinguished direction.

 

[Khashishi]

Waves don't have to move up and down. For example, sound waves are longitudinal waves, so if you look along the direction of propagation, there are alternating regions of high and low density. You can graph the density profile as a sine wave moving up and down. But, the vertical direction of the graph is not a geometric direction.

Likewise, a beam of electrons is represented by a wavefunction which has components which alternatively increase and decrease along the beam trajectory. They don't move up and down in the geometric sense.

If you are familiar with complex numbers, you might be aware of Euler's formula $e^{ix} = \cos x + i \sin x$. You can visualize a complex exponential as a corkscrew, which is a combination of a sine wave moving up and down and a cosine wave moving left and right. But these directions are not geometric directions, but simply mathematical abstractions. At the risk of oversimplification, the electron beams have shapes like complex exponentials.