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jeremyfiennes
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- In the 2-slit experiment using electrons, what speed do they travel at?
In the 2-slit experiment using electrons, what speed do they travel at?
When you say "the electron is moving at speed ##v##" that's just another way of saying "the group velocity of the wave is ##v##".jeremyfiennes said:So the electron-particles can travel at any speed. What about the electron-wave, that causes the interference?
That's a major misunderstanding about quantum physics. The wave-particle duality is NOT about something being both a wave and a particle. That, as you have noted, would allow one to separate the electron wave and the electron particle, or the light wave and the light particle.jeremyfiennes said:It's a question of the wave-particle duality. Light-as-waves and light-as-particles both travel at the same speed c, so no problem. But electons-as-particles can travel at any speed. My question is: what about the electrons-as-waves that give rise to the interference?
I think the wave-particle duality is still useful to think about, if you think about it in terms of what quantum objects behave like, as opposed to what they are.vanhees71 said:I'd put it more strictly as: Since the discovery of modern quantum mechanics by Born, Jordan, and Heisenberg in 1925 together with Born's probabilitistic interpretation of the quantum state there is no more any wave-particle duality. This intrinsically inconsistent picture of old quantum theory has been overcome with the modern theory, which is consistent.
One should stress that photons are never like point particles. There's no way to localize them at all, because there's not even a position observable you can define for them. This is because the case of massless quantum fields has to be treated separately from the case of massive ones. Massless quantum fields with spin ##\geq 1## do not admit the definition of a position observable in the usual sense and thus should not be interpreted as particles. All you can say about a photon (a Fock state of the em. field with definite photon number 1) is the probability to be detected at place defined by the position of the (of course massive) detector.
For massive fields you can always construct a position operator (no matter which spin), but also here all there is you can define are the probabilities (or probability distribution) for finding a particle at a given place.
The speed of electrons in a 2-slit experiment is important because it affects the interference pattern that is observed. The faster the electrons move, the shorter the wavelength and the more closely spaced the interference fringes will be.
The speed of electrons in a 2-slit experiment can be measured using a variety of techniques such as a cathode ray tube, a scanning electron microscope, or a particle accelerator. These methods involve measuring the time it takes for the electrons to travel a certain distance and using this information to calculate their speed.
No, the speed of electrons does not change when passing through the slits in a 2-slit experiment. However, their direction and wavelength may change, which can affect the interference pattern observed.
Yes, the speed of electrons in a 2-slit experiment can be controlled by adjusting the voltage or current in the experimental setup. This can change the energy of the electrons and therefore their speed.
The speed of electrons in a 2-slit experiment is related to the uncertainty principle, which states that it is impossible to know both the position and momentum of a particle with absolute certainty. In this experiment, the speed of the electrons affects their momentum, which in turn affects their position and the resulting interference pattern.