Tag Info

Hot answers tagged

12

A few years ago the XUV physics group at the AMOLF Institute in Amsterdam were (to my knowledge the first to be) able to directly image the orbitals of excited hydrogen atoms using photoionization microscopy. For more details see the paper, Hydrogen Atoms under Magnification: Direct Observation of the Nodal Structure of Stark States. A.S. Stolodna et al. ...


9

The first images of hydrogen s orbitals were obtained in 2013 by physicists in the Netherlands.


5

There is no such thing as classical motion of an electron in an atom. The quantum states electrons in an atom are in are atomic orbitals, which possess a definite energy, but not a definite position. The Bohr model of the electron, in which electrons are thought of as classical particles orbiting the nucleus, is false. The question whether or not two ...


5

The mass of a fundamental particle turns out to be quite an elusive concept, because massless particles act as a source of gravity and they carry momentum. What then is special about mass? Where mass comes in is in explaining the relationship between the total energy of a particle and its momentum. For any particle we have the expression for the total ...


3

Careful! The essence of your question is a good thought but I think you are having several misconceptions. First of all, it doesn't make sense to talk about a phonon being directed towards a single atom. Phonons are delocalized. Secondly, the "input of temperature required to eject an electron" is a dangerous idea. You need to input energy to eject an ...


3

No, it is not possible. That would violate the conservation of lepton and baryon number.


2

There exist two frameworks in which to look at how fields and interactions appear: a) when talking of elementary particles and their interactions it is the quantum mechanical framework; this is the underlying framework from which emerges b) the classical mechanics and electrodynamics framework. The classical emerges smoothly in a computable way. An ...


2

You are having some misconceptions Wire(more pricisely axle) is not rotated between magnetic field in a turbine generator.Wire(more pricisely axle) is used to rotate an coil (present between magnetic fields) present in generator. Magnetic field itself can not force electrons in a conductor to move untill it is at rest. We need an moving conductor so that a ...


2

Is the working principle of light bulb reversible? No. Electric potential energy is converted into thermal energy in the light bulb filament. At a certain temperature range the filament will light up; that is, it will radiate with a wavelenght in the range of visible light. That this process is non-reversible might be clear if you consider some more ...


2

A classical "shell" of charge of radius $R$ will appear to have a field, outside the shell, corresponding to the charge all being at the center of the shell. If the charge on the shell is $q$ then a charge $dq$ being pulled in from infinity will cost an energy $k_e~q~dq / R$; without loss of generality this is the same if $dq$ is spread over an infinitely ...


2

How quickly discharge will occur in the situation you sketch depends entirely on the surface properties of the negative electrode. For current to flow, electrons need to be released from the negative electrode; once they are free, they will accelerate unimpeded to the positive electrode. They will arrive there with 1.5 eV of energy, causing a small amount of ...


2

There is a grand tradition in electromagnetism to talk about the electric fields using the same terminology as we use for velocity fields. For instance we talk about the flux which rightly is a flow per area (and sometimes we multiply by the area and still call it a flux, which is even more confusing to call two things a flux) but it isn't a flow because it ...


2

If you were holding some charge there with some force and always had then an equal charge would distribute throughout the surface of the conductor so that an equal but opposite charge could be right where you are holding your charge. So it is just like the charge was always distributed on the surface. If however you inserted some charge somewhere really ...


1

The idea of electrons orbiting the nuclus is called the Bohr model and has now been replaced with a quantum model. Electrons exhibit wave-particle duality, which means they sometime act like a wave and sometimes like a particle. They don't actually orbit the nucleus but have areas around it where you are more likely to find them called orbitals. The ...


1

When there is a resonance in electron response, both refractive index and absorption change rapidly: the refractive index has a "jiggle" in the vicinity of the resonance, like this sketch (adapted from this earlier answer by John Rennie - but I disagree with the "n=1" label so I cut it off...: As you can see there is higher refractive index at the low ...


1

Due to gravitational time dilation, for an observer of the planet, the frequency of electromagnetic radiation would be slower. Visible light emitted from the planet would appear as infrared or micro-waves. The amplitude of the radiation would not change. Since frequency decreases while amplitude remains constant, the radiometer would receive less ...


1

In vacuum there are no charge carriers like ions or electrons. With nothing to carry charge, i.e. current, such a battery would discharge much, much slower than when the battery poles are connected by something that can carry charge like a conductor or an imperfect insulator.


1

Lines of electrostatic force exist between the positive and negative poles of the battery, even though they're separated by a vacuum. Vacuum permittivity is ε0 = 8.854 * 10^-12 farads per meter. By convention, this is called the dielectric constant of 1, a baseline against which the dielectric permittivities of other materials are compared. ...


1

Electrons (and other charge carriers, e.g., ions) in vacuum travel without resistance. However, as pointed out, correctly, in the other answers, there are no charge carriers in vacuum. Nevertheless, electrons can escape from the terminals if they have a kinetic energy which is bigger than the potential barrier of the terminal surface, i.e., the work ...


1

Assume that the free space is vacuum and the battery is perfectly insulated as well as all the electrical contacts. In this case there are two possibilities for an electronic device to fail: 1. The induced emf in the inductive elements of electronics device because of the changing electrical field caused by the addition of electrons. 2. Most of the ...


1

The metal plate is typically attached to a circuit which collects the ejected electrons making the system net neutral overall just with a current flowing. Also they are usually more easily ejected because the plate is at a potential attached to a battery. However, if the plate were suspended by an insulator in a vacuum and it continuously lost electrons ...


1

From classical models, the electron and a proton revolve around their mutual center of mass, which approximately lies on the proton itself, because the proton has a significantly higher mass than the electron. This is why electrons revolve "around" the proton, and hence form the outer layer of an atom. Quantum mechanically, electrons could never form a ...


1

If I understand your questions correctly: Yes, it can be somehow the other way around. But we do "know": There are two sort of particles in here, one of them has a certain charge and is light, the other has the opposite charge and is heavy. You can then claim that the heavy ones rather stay in place and the light ones sprint around and make up the current. ...


1

Yes. There are loads of physical processes in which photons are created. It won't be possible to list them all out but well known examples are matter-antimatter annihilation (e.g. electron-positron annihilation, at lower energies.), the acceleration of charged particles, radioactive decay (notably, Gamma Decay), etc.


1

Yes, and a good example of this is (or rather was) the LEP collider that preceded the LHC. This collided electrons with positrons, so it was a matter-antimatter collider just as you say, and the collisions created all sorts of particles including electrons and protons. However, there are several symmetries that, as far as we know, have to be obeyed. Two of ...


1

The hyperphysics site you mention states spin rate of some $10^{32}$ radian/s would be required to match the observed angular momentum. Classical angular momentum is calculated as $I\omega$, where $I = \frac{2}{5}mr^2$ for a sphere. The mass of an electron is $9.11\times10^{-31}$ kg and the site mentions an upper limit of $10^{-3}$ fermis or $10^{-18}$ ...


1

It is not enough for it to be moving - it needs to accelerate (or decelerate). An accelerating charged particle will emit radiation and it will lose energy as a result. An excellent example would be the loss of energy of charged particle in synchrotron accelerators. They emit... synchrotron radiation. This is either a boon (e.g. the Diamond light facility ...



Only top voted, non community-wiki answers of a minimum length are eligible