Photon Definition and 1000 Threads

I'm new here and I'm sure others have asked the same question. I understand viewing a particle of light would involve you using light which wouldn't work. But using your wit and process of elimination you could theorize what a light photon could look like. Once again I'm new and have no serious...

Homework Statement In a Compton scattering experiment, a photon is scattered through an angle of 90.0deg, and the electron is scattered through an angle of 18.3deg. Determine the wavelength of the scattered photon 2. Relevant equation The Attempt at a Solution [/B]I'm confused. I...

When a photon is emitted by an atom is the energy of the atom conserved?

is a photon a particle? Tex

Assume a very large volume of a gas of a specific molecule. This molecule can absorb a photon and spontaneously quickly re-emit a photon of the same energy before the molecule can physically interact with another molecule. Therefore the energy of these photons never participate in the...

In introductory physics and chemistry, photon excitation is usually illstrated with a simple hydrogen molecule. I am wondering what happens if an electron is excited to an orbital that is already full. Would the orbital split up into different energy levels as hybridisation, so as not to violate...

From classical electrodynamics textbooks, we know that the Fizeau experiment supports relativistic 4-velocity addition rule. But a recently-published paper says that the photon does not have a 4-velocity. See: "Self-consistent theory for a plane wave in a moving medium and light-momentum...

If photons are the force carrier of the EM force, and they have no charge, how do they give the information between two charged particles? How would a proton know the difference between a electron and positron?

If the energy of a photon: Ephoton = hν, where h = Planck's constant, and E = mc2, then does hv = mc2 And if so, if c=vλ: Ephoton = hc/λ = mc2 Thus mass: m = h/λc ?

Homework Statement Electron with KE = 50eV is captured by Alpha particle, ie. HE++. Calculate the frequency of the emitted photon. Homework Equations KE = m/2 v^2; E=hf, En = Z^2*-13.6eV/n^2 The Attempt at a Solution Energy before = Energy after 50eV = 4*-13.6eV/1 + hf f = 1200nm

This is a very fundamental question. I apologize for its simplicity. I did searches on the web but could not find a clear explanation. Whenever I read about the principles of quantum physics, I always come across a statement along the lines of: "electromagnetic energy could be emitted only in...

Homework Statement A high energy photon moving to the right strikes a proton that is moving to the right at a speed u/c= 0.40 in the laboratory frame, creating a proton and a neutron: γ + p → p + n For the purposes of this question, assume that protons and neutrons have an equal mass m. a) What...

In an earlier thread of mine, another physics forums member was nice enough to point out that there is an uncertainty relation between photon number and wave phase for light. https://www.physicsforums.com/threads/is-there-a-frequency-eigenstate-for-light.727141/ Now I am wondering, where does...

I have a question about photons and the Schrödinger equation. Photons behave like particles but also as waves. I understand that this can be described by the Schrödinger equation as a photon having a certain probability to be somewhere. If I understand this correctly, I take it that there are...

I am really stuck at this question. I tried to get the equation of volume with independent variables P and T, but the equation itself does not give a nice form, and thus I cannot get the derivative of V with respect to P. What should I do?

Hi, I'm having trouble answering Question 9.20 in Hobson's book (Link: http://tinyurl.com/pjsymtd). This asks to prove that a photon will just graze the surface of a massive sphere if the impact parameter is b = r(\frac{r}{r-2\mu})^\frac{1}{2} So far I have used the geodeisic equations...

String Theory speculates that extra dimensions may exist. Obviously, it would be difficult to describe or imagine that, but is it possible that there are objects or particles that exist observing LESS dimensions. For example, photons travel at c meaning that time travels infinitely slow in for...

I've been searching around the web to figure out why photons shift towards the longer wavelengths as they travel from stars and other light sources but I haven't figured out why they loose energy as they travel ( and after reading some web pages I was told that they don't even loose the energy...

This is my very first post, so here it goes. I've had this idea for a while but this is my first attempt at putting it into words. We've all heard of the hypothetical demonstration that tries to put gravity into perspective by pitting a fired bullet against a simple falling bullet. The idea...

Homework Statement Linearly polarized light of wavelength 5890 A is incident normally on a birefringent crystal that has its optic axis parallel to the face of the crystal, along the x axis. If the incident light is polarized at an angle of 45° to the x and y axes, what is the probability that...

I have been trying to better understand the concept of a photon (I know...a thousand threads on this alone) and the direction that it propagates. I understand the time-varying field explanation for em waves, but here is where I break down. If an electric field extends in all directions...

bcrowell wrote: "Lorentz contraction doesn't describe what we see. When we see things, that's an optical measurement. Relativistic optics is a whole separate subject. Lorentz contraction describes the results of the kind of elaborate surveying process that we have to undertake in order to lay...

What happens if a photon, photon b, interacts with a slower another photon, photon a, which is in front? Taking in account that these two photons are identical except for their speed, they are on the same path and direction as well.

Assuming that your surface temperature is 99.1 F and that you are an ideal blackbody radiator (you are close), find (a) the wavelength at which your spectral radiancy is maximum,(b) the power at which you emit thermal radiation in a wavelength range of 1.0 nm at that wavelength, from a surface...

Homework Statement [/B] The problem on where the photon will hit a screen, after passing through a single horizontal slit. I know the wavelength, slit width, magnitude of momentum of incoming photon (calculated), and distance between screen and slit. Homework Equations I just don't...

In 'an introduction to quantum field theory' by peskin, he writes: To analyze the photon one-point function, note that the external photon must be attached to a QED vertex. Neglecting the external photon propagator, this amplitude is therefore: I really cannot justify this equation. Can...

Hello. I'm studying quantization of electromagnetic field (to see photon!) and on the way to reach harmonic oscillator Hamiltonian as a final stage, sudden transition that the Fourier components of vector potential A become quantum operators is observed. (See...

Homework Statement Hi everybody. I have to demostrate that a photon, no matter it's energy, will never be able to create a positron and an electron on it's own. Homework Equations E=Sqrt(m^2+p^2) as long as c=1 Conservation of energy Ei=Ef; initial energy is equal to final energy...

I’ve seen references on here to photons being “excitations of the EM field”. I have a few questions about those “excitations”. I assume they are eigen-solutions of the 1D wave equation?What are the boundary conditions on the solutions?Is a single photon a single eigen-mode, or a supper-position...

If I produced a material that neither absorbed nor reflected light. Or at least did so to an extremely miniscule amount and set it in space and hit it with light. Would there be any thrust imparted unto it? If so would it be significant? My initial thoughts would be that sense it is massless...

Reading an old thread (wich is now closed or i would post the question there) there was a discussion about the size of a photon, and if it was an adequate question at all. The discussion on the other thread couldn't agree on a response. Yet there was some postulates that could work with this...

Do different photons with different frequencies/energies have same magnetic field? Does the fact that all photons have same magnetic angular momentum imply a positive answer?

Hi, Im in my final undergraduate year of a physics major. I need to prepare a short presentation for "The mass of a photon" in my theoretical physics class. I do not do particle physics at a high level, so I don't have much experience in this field. Can anyone recommend me a source or key...

Is there any experimental evidence that photons can transmit negative momentum? After all, there is also a negative root: E^2 = (pc)^2 + (mc^2)^2

When two photons' spins are entangled, measuring one spin gives you the spin of the other. My question is, after one of the particles is measured, does it still retain its entanglement? Could you keep measuring photon A's spin to get photon B's spin?

Why do we say gravity [GR] is a theory about ‘spacetime curvature’ and gravitational waves are ‘ripples’ but nobody uses such a description for electromagnetic fields? Don't EM waves 'ripple' spacetime? For example, one might imagine different types of spacetime curvature associated with each...

According to Hawking [1] it is posited that light photons at the event horizon of a black hole must cease to move, and remain motionless for the entire lifetime of the black hole. It is also observed [http://dls.physics.ucdavis.edu/~scranton/LensedCMB/a2218.gif] (and calculated) that the path...

Hi. We can write a polarised photon as ##\left|\alpha\right\rangle=\cos(\alpha)\left|\updownarrow\right\rangle+\sin(\alpha)\left|\leftrightarrow\right\rangle##. Trigonometry gives us $$\left\langle\alpha | \beta\right\rangle=\cos(\alpha)\cos(\beta)+\sin(\alpha)\sin(\beta)=\cos(\alpha-\beta)$$...

[Moderator's note: Spun off from another thread, where it was off topic. Please start a new thread when you have questions on a new topic.] Photons lose energy when they travel long distances. Where does that energy go? What happens to that energy? Is there any theory regarding this?

Suppose we have a creation point C where two entangled photons A en B are produced. 1m in the direction of A is a vertically polarized filter V. 2m in the direction of B is a horizontal polarized filter H. Now, I understand that when photon A strikes filter V, it either gets blocked or gets...

Hi All, Is there any experimental evidence that photons may have attached to itself a coherence length? Best Regards, DaTario

I am interested in what the recoil velocity of an initially stationary hydrogen atom in free space would be when it emits a Lyman alpha photon. I tried to do the calc and got about 3 metres per second which seems rather high.

The results of the double slit experiment lead to the conclusion that a photon travels as a wave. Question 1: Is it possible to track the journey of the photon? It seems to me (correct me if I'm wrong) that from the moment we release the photon till contact with the detector we don't know what...

Dear All: I'm trying to use fluctuation dissipation theorem to describe spontaneous photon emission process by electron-hole recombination in semiconductor material. I notice that all the references using such a method considers the dipole's degree of freedom separately, for example in x, y, z...

I am looking for group of material that behaves according to the following: (1) When a certain laser light passes perpendicular to the surface of the material it enters and exits unimpeded (2) However, when another laser light (with direction parallel to the surface) enters the material, the...

Has there ever been any detection of a pulse of light spreading out longitudinally even by an infinitesimal amount? I'm aware of the expansion of space (~74 km/sec/Mpc), but talking about something else. So for example if our light pulse is say one second in duration, then after traveling...

I can't find this in any textbook, so I must not understand something about it. What is the Lagrangian of a photon? Would it be just h*nu?

Homework Statement If an electron in metallic cesium absorbs a photon of red light (6.6x10^-7) m in vacuum), all the energy is used up in escaping from the attractive forces in the metal. Suppose light with 5x10^-7 is used, what percentage of the photon's energy does the electron retain after...

Homework Statement I am preparing a report on black holes and I recently learned about a phenomenon I was previously unaware of: the photon sphere of a black hole. While reading an article on said occurrence (I have now confirmed this on multiple sources) the photon sphere which is the minimum...

Is this statement correct: ? "The effect of making this observation is to force the photon entirely into the state of parallel or entirely into the state of perpendicular polarization." * I don't see how you can talk about how the polarization of a photon changes if the photon gets absorbed...