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7

First, the electron is not a point particle. The abstraction you are thinking of is what we would call a naked electron. In an experiment, you do not see the naked particle ever. It is always surrounded by virtual pairs. Hence, what you measure as the electron is really a many-body system. Second, you might want to read this. The take-home message is "the ...


6

First, there is nothing wrong with our charge polarity conventions. They are predict electrical phenomena just as accurately as the opposite convention would have done. Did we have a problem if since the begin of their discovery we called them positive particles and negative to protons? We could predict the behavior of electrical phenomena equally ...


6

There is no universally accepted quantum theory of gravity. Quantumly, the "shape" of a fundamental particle is a very fuzzy notion - we know that states are often not localized, so it is wholly unclear what it means to say "the electron is pointlike". The proper formal interpretation of a "pointlike particle" is simply a particle that is not composite - ...


5

In our modern understanding, every electron is thought to be a localized excitation of the electron (or Dirac) (spinor) field $\Psi(x^\mu)$, while every photon is considered to be an excitation of the photon (vector) field $A^\nu(x^\mu)$, which is the quantum field-theoretic counterpart of the classical four-potential. Thus, the answer to your questions ...


3

You have fallen prey to a popular simplification of spinors. The statement "you have to turn electron by 720 degrees in order to get the same spin state" does not refer to an actual rotation of an actual electron. In quantum mechanics, we describe the states of objects as elements of a Hilbert space $\mathcal{H}$. The crucial thing is that not all elements ...


3

The non-negative real probability distribution can't interfere like a complex wave function can. To produce interference phenomena it is necessary for quantum mechanics to deal with probability amplitudes, not just probabilities.


3

You say that we are only interested in the probability distribution on the screen, $\rho(x,t) = \lvert \psi(x,t) \rvert^2$, which is essentially correct. So, why do we have $\psi(x,t) = \lvert\psi(x,t)\rvert\mathrm{e}^{\frac{\mathrm{i}}{\hbar}S(x,t)}$? Well, looking at the time evolution equation for the probability density, the continuity equation of ...


3

You are probably thinking in terms of the shell model of the atom: (source) It is important to note that the shell model is ultimately inaccurate and is not really a good representation of how modern physics views atomic structure. It has a few advantages, and it is a nice tool to explain certain features in atomic structure (in particular, the fact that ...


3

If the photon is massless, how can it make an electron change momentum? Because, relativistically, momentum isn't proportional to (invariant) mass? Thus, particles with zero invariant mass can have non-zero momentum.


3

First of all, two isolated protons cannot fuse to form a bound state. The nuclear force between nucleons depends on their spin orientation. It is too weak to bind two nucleons with anti-aligned spins and two identical nucleons (two protons) cannot be bound with identical spins because of the Pauli exclusion principle. The nuclear force is a residual of the ...


2

Exactly what is this "circuitous route"? Does the thing I touch also have to be touching the carpet? Though I'm not a native English speaker I am pretty sure that a circuitous route is a path that combines you shoes and the carpet as were they a part of a circuit. The thing you touch has to be connected to the carpet (by touching the carpet itself or ...


2

We do consider that energy. It reduces the amount of energy needed for the electron to be freed from the surface. An analogy: If a satellite is already in orbit, you need less energy to make it escape earth's gravity than if you started with the satellite on a launch pad on earth. The energy of the satellite in orbit is like the energy of the electron ...


2

Nice question. This is connected to gauge invariance. The interaction term in the Lagrangian (interaction between charge and field) is not gauge invariant. Thus, a curl-free vector potential, which corresponds to zero magnetic field, appears to have a non-zero momentum. Nevertheless the equation of motion is not changed in a new gauge, i.e., you will get ...


2

The simplest example I can think of to illustrate this is the spectrum of the hydrogen atom. The excitation of the electron from the ground state, n = 1 produces a series of absorptions known as the Lyman series. The first line is excitation of the electron from n = 1 to n = 2, the second line is n = 1 to n = 3 and so on. But there are also absorptions due ...


2

Multielectron atom has much more complex energy spectrum than hydrogen atom. As the electrons interact with each other, the hydrogenic energy levels get shifted, and much of the hydrogen-specific degeneracy, as well as degeneracy resulting from electrons mass&charge equality, is lifted. Moreover, since the electrons do interact with each other, we can't, ...


2

An electric current is the flow of electric charge. But electric charge is not an entity, it is a property that must be 'carried' by a charge carrier. An electron current, the flow of electrons, contributes to an electric current since the electron 'carries' negative electric charge. However, an electric current is not necessarily an electron current. ...


1

If you have current flowing one way through a resistor, then the electrons flow through the other way. Since current flows from the high voltage end of a resistor to the low voltage end, then the electrons come in at the low voltage end and come out at the high voltage end. When electrons (which are negatively charged) go from low voltage to high voltage, ...


1

(Moving this from my comment to an answer) Yes, the electric field simply penetrates the glass wall and charges (the electrons) placed in that field will feel a force and move. The glass does not really interact with the charges on either side, so you might as well remove it completely (theoretically).


1

Assuming our only aim is to solve double slit experiment (or other problems that can be mapped into that). Actually the double slit experiment for electrons is a derivative/prediction from the quantum mechanical theory as it started with the Schrodinger equation ,its wavefunction solutions and the interpretation of differential operators with energy ...


1

The answer to your question is yes and there are experiments which use multiple excitations. A very famous one is the Lamb-Rutherford-Experiment where they could prove the existence of the lamb shift. First they excited a beam of hydrogen atoms which were in the $1S_{1/2}$ groundstate into the $2S_{1/2}$ state by bombarding them with electrons. This has a ...


1

The electron gun produces electrons by heating the cathode; this shakes out electrons from the metal ("boils them off"), and as soon as they're out, they are repelled and accelerate away to do your bidding. This is called Thermionic Emission. When an electron is emitted, another one comes in from the cable connecting the cathode to the power source. The ...


1

As almost always, the positive charge in an electric circuit component comes from the positively charged atoms of the conducting metal. The electrons move away from the plate that is to be positively charged (towards the positive pole of the voltage source with which the capacitor is being charged), and hence there is a net positive charge on the plate, ...


1

if protons can be forced to fuse, can electrons technically fuse too I'm not aware of any known mechanism by which two electrons can 'fuse'. It is possible, however, for two electrons to form a Cooper pair which is the basis for superconductivity. However, this cannot occur between two otherwise isolated electrons.


1

There are two kinds of momentum. One kind is simply a frame dependant portion of a larger tensor. It is exemplified in the total stress-energy tensor, which is a symmetric rank two tensor that is divergence free. The divergence free part means that is is conserved locally in in the sense that the momentum (or energy) in a region at one time, is equal ...


1

In a (perfect) semiconductor, there are no electronic states available in the band gap. Therefore, despite the fact that the Fermi-Dirac distribution "predicts" (or better: accounts for) electrons with energies lying in the band gap, they cannot exist there because no states are available. If the Fermi level lies in the band gap, the undoped semiconductor ...


1

There are two important contributions: First the density of states, which tells you the states, which can potentially be occupied. Then there is the Fermi-Dirac distribution, which tells you, which energies are occupied. The Fermi-Dirac distribution does not include allowed and forbidden states. You must fold it with the density of states, which is then ...


1

The micro world of atoms and molecules is ruled by quantum mechanics. The forces controlling the interactions between them at the level affecting everyday situations, as touching, are electromagnetic. In quantum mechanics the electrons are in bound states around the atoms, and at most can be mobile in bands when in a solid, i.e a bound state due to the ...


1

Since you don't have velocity information on the electron, then it doesn't have momentum, so any equation involving p can't be used. Just convert the electron's rest mass to energy directly, using E=mc²



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