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Posts posted by Sato

  1. Repel is not a word I would use, because this does not take place like electrostatic repulsion, which varies with distance (1/r^2). Electrons scatter photons. Compton scattering happens http://en.wikipedia.org/wiki/Compton_scattering


    I have read through that article as well as others on the topic of scattering theory but my comprehension rate was not very high, I think due to the concentration of jargon on the wikis. How would you describe it?

  2. The universe is composed of mass-energy + dark matter + dark energy. However, we do not know what any of these things are. Is any of it real, or is everything a hologram. For sure, nothing is as it appears. Everything we see can be sucked into a black hole, then cannot be seen.



    You look like Dr. Susskind in your profile picture:


  3. No. There's nothing like electrostatic repulsion going on.


    Free electrons can't absorb photons. Either energy or momentum would not be conserved; it's a nice little exercise for those learning this level of physics to show this.


    Oh okay, unfortunately I do not think I am at that level yet.

    If it's not like that, then what causes the photon to scatter away from the electron?

  4. Not really the same thing. Photon absorption by an atom has a delay, which is the lifetime of the excited state, and emission in a particular pattern. In electron scattering (Compton scattering) there is no excited state and the scattering angle has a different pattern and a wavelength shift that depends on the scattering angle.


    Since the electron does not absorb the photon, and a photon still exists, there is no change in the spin orientation of the electron. Angular momentum is conserved.


    Would the electron repel the photon as if it had the same charge? And is it impossible for free electrons to absorb photons?

  5. Electrons can be free, and they do not have quantized energy states when that's the case. They scatter photons, but do not absorb them. Their tracks can be recorded (e.g. in a bubble chamber), but in general their location is difficult to pin down.


    Isn't scattering the absorption and emission of photons? If not, please correct me.

    So does the free electrons' having no quantized energy states mean that all free electrons are accessible and their orientations can be changed by photons of all energies/wavelengths?

  6. Yes. This is the same reason why neon lights (or other gas discharges) emit a particular color.


    Oh okay, I see. Thank you! But alas, my curiosity on this topic has extended since the preceding Q&A:


    - Can electrons be free, not harnessed by nuclear forces? Like neutron degenerate matter, but for electrons?

    - If so, are the distinctions of orbitals and energy levels still applicable?

    - Can their positions be tracked in a vacuum, using some form of spectroscopy?

  7. No. All transitions in an atom are quantized, so the energy has to match the transition, and the angular momentum state has to be accessible. There are transitions that are forbidden because it would violate conservation of angular momentum.


    Does that mean it's such that there are wavelengths that will only affect or be able to access electrons of a certain energy or orbital?

  8. Orbital and energy level are separate things. Energy level is the principle quantum number, n. Orbitals are the orbital angular momentum quantum number. The S orbital and P orbital in Hydrogen's n=2 excited state differ by their angular momentum (S has 0, P has 1 unit). In the basic solution of the Schrödinger equation, their energy is the same (in QM parlance, they are degenerate states). In reality, there is more going on and the interactions are subtly different, which shifts the energy of each a small amount, or "lifts the degeneracy" (this is the Lamb shift)



    Yes. A photon has 1 unit of angular momentum, and a spin flip changes angular momentum by 1 unit.


    And will this happen the same way when a photon is absorbed no matter the wavelength/energy of the photon or energy state of the electron?


    An electron has spin 1/2, but can be spin "up" or spin "down", which is the orientation (technically the z-axis projection of the spin) given by ms . ms = ± 1/2


    And it gets more complicated than that. When you have composite systems, you look at the total angular momentum, which can be several units of Planck's constant. There, the combination of orbital angular momentum (l) and spin (s) give j. j is no larger than l+s, but it can be smaller (i.e. s= 1/2. if l=1, j can be 1/2 or 3/2). This total angular momentum now has a projection, mj, and -j =< mj =< j


    Then you add in the nucleus, which also has a spin (I). F = (I) + j


    All of that is for a single energy level (principle quantum number) of an electron.


    So, a photon can change the orientation (up or down) of the electron right?

  10. Sorry, I am slightly dyslexic and sometimes misread. I do not know if it is resonant or not, but is certainly inductive coupling. As I recall resonance requires a tuned circuit, and whether the circuit in question is tuned to the primary frequency (e.g., 60Hz) or a harmonic depends on the inductance and capacitance within the circuit. More energy would be transferred if the circuit is resonant to the primary frequency or within a couple of octaves, but some energy would transfer in any case.


    Oh okay, thank you!

  11. I was referring to swansont's post mentioning orientation.

    The amount of spin of an electron is always the same. The orientation of it can change.


    Is moving to a different orbital what he was talking about?


    And does the change in orbital depend on the state the electron is currently in or the energy/wavelength of the photon?

  12. tyvm

    In answer to the topic question, "How close to a generator do I need to be?" One can only guess, but it would have to be fairly close, and depends on several factors including the type of generator, the battery voltage, and circuit construction.


    Is tyvm another way of saying yes? I wasn't sure so I was asking if that's what it's called.

  13. No, you're quite right, and Brett is wrong. Photons have no charge and do not interact with each other.


    When an electron absorbs a photon, it becomes excited and it goes up to the next orbital level. The electron can fall back to the lower orbital by emitting a photon..


    Thank you, I thought something was off about what he said, as it also contradicted ajb.


    If anyone can answer my other question too:

    So a photon can change the orientation of the electron? If so, is this definite or does whether the orientation changes depend on the energy state of the electron or photon?

  14. No, they cannot occupy the same space, nor will they. they are repulsed by each other, the same as ions. of course, if you were to emit a lot of ions in a small space, then you could force them into the same space? no! they have no mass so will travel, anyway they can, to another point in the universe. photons will have a charge, and that charge will repulse other charges, as they are the same - like with magnetism.


    If a photon is absorbed by an electron, it will affect the spin by way of it's charges, as they are different from each other, and, absorbing the same space, could alter the spin, at least...


    Yes, if you have a different formula, you will have a different result. how can you take fingerprints and expect them to be the same?


    I'm quite sure that photons don't have charge, unless that's a misconception?

  15. There is much to speculate about here, but the principle is clear. Magnetic lines from a generator will surround the generator; although, they will be weak compared to inside the generator. The magnetic field external to the generator will generate currents in nearby wiring circuits. A diode in the circuit will create DC current and can charge a battery.


    Ed, is wireless charging like this what is called resonant inductive coupling?

  16. It is the fact that photons are bosons rather than they are massless that allow them to occupy the same space. A little more tachnically, we have what is known as a Bose-Einstein condensate, which is when under the right conditions a large proprtion of the bosons in an ensemble will occupy the ground state.





    You have conservation of angular momentum and spin.




    This depends on what you mean exactly. The short answer is no, but be aware of the photoelectric effect.


    Thank you.



    The amount of spin of an electron is always the same. The orientation of it can change.


    So a photon can change the orientation of the electron? If so, is this definite or does whether the orientation changes depend on the energy state of the electron or photon?

  17. No, it would likely not be a replica of a human brain, and it would never know those senses therefore not feeling any sorrow for not having them. Albeit I'd assume a large-scale AI system like that would implement image and audio recognition as well, but there's no need to worry about it feeling lonely as it wouldn't be conditioned to be used to being around others.

  18. D-Wave Systems recently released their D-Wave Two quantum computer, purchased for use by Google and NASA. The machine is designed to run only certain types of algorithms and is therefore limited in its problem solving abilities, but for those problems which it can be applied, it processes approximately 3200x faster than any classical computer and runs on a 512 qubit register. Of course, this costs many millions of dollars to develop, as stated it can only process certain types of algorithms, and it must be kept cooled to very low temperatures making it of very limited use. What do you think will be the implications of the D-Wave Two, as well as what it may mean for the future progress of quantum computing?


    Here's a link to a BBC article about it:


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