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181

Imagine you are an electron. You have decided you have lived long enough, and wish to decay. What are your options, here? Gell-Mann said that in particle physics, "whatever is not forbidden is mandatory," so if we can identify something you can decay to, you should do that. We'll go to your own rest frame--any decay you can do has to occur in all reference ...


34

The statement is true for decays, where lifetimes can be measured. It is not true for interactions though. A suicidal electron meeting a positron has a good probability to disappear, together with the positron, into two gamma rays, at low energies. Electron-positron annihilation It is intriguing that this is not true for neutrinos. If an electron ...


12

This is not exactly true. It is believed that net charge is conserved, but there is a weak process called electron capture, where an electron is captured by a nucleus, (usually from an inner "orbital" so there is a spectroscopic signature), a neutrino is emitted and a proton changes to a neutron. So therefore your textbook is wrong!


5

An atomic species defined by its number of protons (usually denoted $Z$) and its number of neutrons (usually denoted $N$) is called a nuclide. For atomic species the number of electrons is the same as the number of protons (i.e. $Z$). You are right to assume that the nuclide of a single nuclide solid will typically determine its melting point and hardness ...


4

Depending on your view, there is electronics with other charge carriers. It is commonplace to have semiconductor devices where the relevant carriers are holes! Furthermore, batteries and electrolysis relies heavily on ions as charge carriers (but hardly count as electronics). I guess genuine electronics with ions will be difficult as charge carrier mobility ...


3

The water droplets that create a rainbow are not emitting the light that you see in a rainbow; if they were, you would see a glowing cloud of consistent color, not a rainbow. The rainbow is formed by sunlight refracting and reflecting through water droplets in the air; the water refracts through the "front" of the drop, reflects off the "back," and refracts ...


3

I used to make X-ray tubes for a living... and the "right" answer to this question would run the length of a book. So just a few pointers. I don't expect that you would be able to create an electron tube after this - at least not one that lasts. Note also that if you do get it to work, it will produce dangerous (X ray) radiation. And unless you understand ...


3

That is true indeed. A hole has no physical existence. It is just the absence of an electron that creates the illusion of a positive charge at that point. You can find it in Boylested Electronic Devices and Circuit Theory that it's a theoretical thing.


3

Atoms and molecules that have high boiling points and melting points have strong intermolecular bonds that resist form change. Therefore, to make a material win these properties, in general your you want long chained molecules.


2

It's not even that simple, as different crystal structures of a given molecule can have different melting points, e.g. Ice-V . I don't remember enough solid-state physics to state whether any elements form different crystal structures with different melting points, but certainly, for example, the hardness of carbon depends on whether it's diamond or ...


2

Depending on the location of the switch, the answer will change. A properly wired lamp would have no signal on the live (phase) wire, and therefore there would be no field. However, if you interrupt the neutral wire (or the switch is in the lamp, not the wall) then you will have a varying AC field because the voltage on the wire changes (and thus a small ...


2

You say the lamp is plugged into a AC outlet, but then talk of a "wall switch". Apparently you mean that this switch controls the power to the outlet, and that a switch on the lamp is kept on, or that the lamp has no switch. If so, you should clarify this as a switched AC outlet, since most aren't. In the case of a switched AC outlet, the switch will be ...


2

The blue glow is cause by free electrons (i.e. those not bound in atoms) colliding with some residual gas molecules in the tube. Even though it's under vacuum, there is still some gas present (perhaps even designed this way, to create the lighting effect). In a collision, the gas molecule can absorb some energy from the electron and undergo an electronic ...


2

Regarding your first two points: The symmetry axis of an orbital is free for a free atom. If it's bound to some other atom through one of these one-dimensionally elongated orbitals, the orientation of one orbital is fixed. If you take e.g. carbon, silicon or germanium, you have one s orbital and three p orbitals, which are oriented perpendicular to each ...


2

Ok, the previous answer by Alchemist is totally reasonable, but I think we could add a bit of "what is real?" into this discussion without getting metaphysical. A hole is a perfectly well-defined mathematical concept, in the same way that an electron is a perfectly well-defined mathematical concept. The mathematical concept of an electron in the theory of ...


2

Can we have electronics with charge carriers OTHER than electrons? Yes, see what Sebastian said above. And see the physicsworld article Taming light at the nanoscale: "Look around, and you will probably see numerous electronic and optical gadgets, such as mobile phones, personal digital assistants, laptops, TVs and digital cameras. These may all do ...


1

No. As has been said, the raindrop is not emitting the light, it is just acting as an optical device that deflects light emitted by the sun. However, the spectral lines you would expect to see in sunlight refracted by a prism will not, repeat NOT, be seen. The mechanism that produces rainbows is very different than the mechanism that produces a spectrum ...


1

Presumably you are referring to semiconductors. A hole physically exists in that it is the absence of an electron. Just like a hole in a piece of paper physically exists. However, if you are asking whether the hole is a particle, then no, it does not physically exist. In a semiconductor, we deal with electron hole pair (EHP) generation. When this happens, ...


1

Electrons move quickly because they have low inertia. Their mass is so low that a small push gets them to a high speed.


1

Angular momentum is a conserved quantity (in a closed system) and this is true also for the angular momentum that is carried by the electromagnetic (EM) field. This conservation is a manifestation of rotational symmetry and the azimuthal part of the EM field emitted must be single valued. In other words, when rotating the EM field in the azimuthal ($\phi$) ...


1

What's the effect of a resistor? It's a component that dissipates energy end thus lowers the voltage. So what is voltage? It's the strength of the field that moves the electrons, while current represents the number of electrons flowing through the wire. Free electrons can be stopped all together or slowed all together, but it's not possible to select only ...


1

The situation is entirely different from the double slit experiment! In the double slit experiment, one electron propagates through the slits, its parts interfere, thus we have a density matrix like (this prepares a pure state $\lvert\psi\rangle = \frac{1}{\sqrt{2}} (\lvert 1 \rangle + \lvert 2 \rangle)$): $$ \rho = \frac 1 2 \begin{pmatrix} 1 & 1 \\ 1 ...


1

$$ \newcommand{\ket}[1]{| #1 \rangle} $$ I'll try to answer the last two. with an arbitrary superposition, the probability density for the electron could be anything - can we actually find the coefficients of the superposition an electron actually is in? I'm a little confused about what you mean here. If we are given $\ket{\psi}$ as a combination of, ...


1

HyperLuminal asked: "Does that mean that electrons are infinitely stable?" Think about Dirac's model of an electron, which includes left and right handed contributions. Now add the (Nobel-worthy) Brout-Englert-Higgs idea, that the left-handed bit interacts with a condensate of weak hypercharge, while the right-handed bit does not. This suggests a ...


1

there are various databases for this sort of information. In your position I would start with http://www.vamdc.eu/ which has links to other databases and is currently maintained. It may have more information on molecules than on atoms, but I hope it is useful. Another database is Gaphyor, but an issue with this database is that it does not accept new ...


1

Chemistry as we know it would not exist if electrons were Bosons, because many of the details of the chemical "bonding" of atoms are strongly affected by the requirement that the overall wavefunction of all the electrons involved be anti-symmetric. This anti-symmetrization principle (which is the basis of the "Pauli Exclusion Principle") along with the fact ...


1

Any sufficiently fast particle can go through the atom since the repulsing force is finite and you can prepare a projectile with a high enough energy.


1

The electrons are in random motion within the cord even when it is plugged and not switched on. The motion of the electrons in this is case is random i.e., there is no preferred direction of motion of electrons or vector sum of all the thermal velocities is zero. Each electron within this conductor acts like a point source of electric filed and these micro ...


1

The answer to As an electron drops from a higher energy level to a lower energy level, can it be modeled as a the continuous movement of a charged body, therefore causing a magnetic field to be generated around it? is "Yes, but only trivially." That is, you could probably work backwards from the far-field radiation to some imagined moving source ...



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