Photon Definition and 1000 Threads

In Example 41.5, they are implying that, for a hydrogen atom, if the orbital quantum number ##l## goes down the electron will lose energy. However, they said nothing about the principal quantum number ##n## going down, so there should be no loss in energy. As far as this book has presented, the...

Light is propagating electric and magnetic fields. The electric field interacts with electrically charged particles, e.g. electrons. Is there a corresponding magnetic interaction?

The photon and the gluon in the Standard Model do not interact with the Higgs field and are hence massless and travel at the speed of light. Is there a simple explanation why these two elementary particles are the exceptions?

After conducting the photon interference experiment, below is a sample data of what we got: Time (s) Angle (V) Two-slit Diode (V) 0 0.988 0.203 0.102 0.984 0.297 0.805 0.976 0.398 1.201 0.974 0.5014 1.31 0.968 0.526 The above list goes on for quite a few columns...

Velocity of photon allways is c(photon is massless particle).While velocity of EM wave in medium < c.So does velocity of photon need not allways equal velocity of EM wave?

I am studying the 'toy' Lagrangian (Quantum Field Theory In a Nutshell by A.Zee). $$\mathcal{L} = - \frac{1}{4} F_{\mu \nu}F^{\mu \nu} + \frac{m^2}{2}A_{\mu}A^{\mu}$$ Which assumes a massive photon (which is of course not what it is experimentally observed; photons are massless). The...

I was viewing this video in which the narrator says that the energy of a photon that could discern a Planck length would require a photon of such high energy that it would be a de factor black hole. Is this accurate?

First I'll explain my understanding, because I'm not very confident in it. The main point is that the electrons are ejected and then accelerated to a very high kinetic energy. Then they start smashing into the anode. Most will go through a series of collisions before completely stopping, so that...

When double-slit experimenters say an interference pattern is obtained even when only one photon at a time is fired at the slits, how do they know it was only one? The same when a photon detector is said to respond to single photons.

I set up this problem this way: ##p_a^{\mu}=(E, \sqrt{E^2-m^2}, 0, 0)## ##p_b^{\mu}=(m, 0, 0, 0)## ##p_c^{\mu}=(2E_\gamma, 2E_\gamma, 0, 0)## I have chosen to consider the two photons as a single particle of energy equal to ##2E_\gamma##. At this point I applied conservation of the...

I am considering the magnitude of the gravitational redshift and I look at the process of a photon leaving an atom from the Sun. I am asking whether the processes in the atom, viewed as a clock, would lead us to conclude that the emitted photon, at the time of emission, would itself be...

Hello! Assuming we have a 2 level system (e.g. an atom with 2 energy levels) and the lifetime of the upper level can be neglected, if we make the atom interact with a laser at a fixed frequency, we would get Rabi oscillations (assume the laser is on resonance). Would we still get Rabi...

Am I right in thinking that all photon detection methods depend on a photon displacing an electron, that then displaces other electrons to give a detectable electric current pulse?

I have a doubt about the first request: I suppose to find the minimum energy of ##\gamma## in the situation where ##p## is stationary, there is no reason to say that the proton is stationary if I were to calculate it in the CM, right?. So I have to consider che LAB-frame to find ##E_\gamma##...

I consider the laboratory system. The four momentums in this reference system are respectively: ##p^\mu = \big(\sqrt{|p|^2+m^2}, 0, 0, |p| \big)## ##p'^\mu= \big(m, 0, 0, 0 \big)## ##k^\mu = E\big(1, 0, 1, 0\big)## ##k'^\mu = E'\big(1, 0, -\sin \varphi, \cos \varphi \big)## I used conservation...

In a given mode with an average number of photons ``##\bar{n}##, the photons are distributed around their average according to the formula $$p_n = e^{-\bar{n}} \frac{\bar{n}^n}{n!}$$ The justification of this formula in quantum field theory involves considering field operators acting on a...

The Sub Photon Sphere Escape (SPSE) Game Game Board: Vast Empty Space Game Pieces: ##\space## 1) A large perfect Schwarzschild black hole ##\space## 2) A Carrier/Trigger. This is a massless device that sets the Player Device into a selected position and velocity and then triggers it...

I've spent well over two hours searching the web for two functions of the radius of a Schwarzschild BH. One would give me the escape velocity of the BH assuming a perfectly vertical trajectory (so it isn't a normal escape velocity). The second relates to the trajectory of a photon that is...

The question arose when watching Sean Carroll video: The Biggest Ideas in the Universe _ Q&A 6 - Spacetime 3:50 - 13:30 Because photons follow null geodesic in spacetime the question arose from viewers: "photons do they really experience no time this is a question" And in the answer: "but if...

Physics is not my area of expertise. That being said, philosophy of science is, but I'm not here to discuss philosophy. I recently found myself trying to imagine how light behaves once it crosses the event horizon of a black hole. Presumably, between the event horizon and the singularity...

I don't really know how to proceed. Can someone help me out in this?

I was just reading about the LIGO experiment wherein an interferometer was used to detect gravity waves. This interferometer uses opposed light waves, detecting if there is a shift in their wavelength due to stretching/squeezing of a gravity wave passing through the lasers. (I hope I'm saying...

Allow me to hijack this thread for a second: a photon is an excitation of the electromagnetic field, right? The photon does not exist until measured. So how can we send a photon in a particular direction, so it has a known position and momentum?

Hi Pf I read that in the light propagator there are loops of electrons. What would be the consequences if we could switch them off (or neglect them)? would it modify the speed of the photons?

I'm trying to think of a how the double slit experiment can detect a photon without interacting with it in theory. In principal (not reality of course) does a photon have a gravitational signature which could be used to detect which slit it traveled through during the double slit experiment...

Hi, Planck's equation is written as E=hν where "E" is energy of a photon, "h" is Planck's constant having value 6.626 070 15 x 10-34 Js, and "ν", Greek letter nu, is frequency. Violet color has frequency range between 790–666 THz (Tera =10^12). If a violet photon of frequency 7.5 x 10^14 Hz...

We all know that Feynman declared wave-particle duality as the central/only problem of quantum physics. Not sure how to evaluate a recent publication summary on this topic: https://sciencex.com/news/2020-11-wave-particle-duality-entanglement-customary-pitfalls.html Would like others take on...

Photons have 0 rest mass. But could I talk about relativistic, or dynamic photon mass, that would be the solution of hf = mc^2 ? The relativistic mass would be m = m0/sqrt(1-v^2/c^2), where m0 is the rest mass, so 0, and v = c, so the denominator is also 0. The previous equations would give 0/0...

Obviously a particle inside an ISW of width L cannot have arbitrarily precise momentum because ΔP ≥ ℏ/2ΔX ≥ ℏ/2L. Therefore you cannot have a particle with arbitrarily low momentum, since that would require ΔP be arbitrarily small. I need to show that a photon inside an ISW cannot have...

How would you explain, on a basic level, why only one photon (as opposed to two, three...) is emitted when an electron in an atom changes its energy level? This is for students with only introductory Physics background.

This question is a followup to another thread. https://www.physicsforums.com/threads/qs-re-the-behavior-of-atoms-after-decoupling-completed.994581/ I would like to explore the issue raised by @kimbyd. . . . after reionization the temperature of the intergalactic medium is dominated by...

Hi all. I have been reading the following article and have a couple of basic questions about the decay of the Higgs into photons process - https://www.physicsforums.com/insights/lhc-part-4-searching-new-particles-decays/ As i understand this decay - the photons will have the same frequency and...

a photon have defined frequency , but we treat it as a localized particle ,how that can be? if i am looking at second quantisation, photons are modes of the electromagnetic field , and they are not localized at all , but we do know that photons are somewhat localized , like in the...

I see that this procedure helps to get rid of the two extra degrees of freedom (due to the scalar and longitudinal photons) one firstly encounters while writing the electromagnetic field theory in a Lorentz-covariant way; it indeed shows that modifying the allowed admixtures of longitudinal and...

A 2015 paper in Nature Communications by M.Fuwa et al arxiv [1412.7790] Experimental Proof of Nonlocal Wavefunction Collapse for a Single Particle Using Homodyne Measurement Authors:Maria Fuwa, Shuntaro Takeda, Marcin Zwierz, Howard M. Wiseman, Akira...

How can a photon have a frequency? Anything moving at the speed of light is predicted to have a zero time rate, e.g. the frequency of a ticking clock would be zero. So no aspect of the light should change along its path - in the same way that no aspect of the moving clock would change. If...

In the original experiment a photon 45 degrees polarized goes through two beamsplitters and comes out 45 degrees polarized and if you measure the individual path, you measure vertical or horizontal. I was just wondering, has the experiment below (or something simular) ever been done? Do we...

I heard there is a saying that photon and light in a certain wave mode are equivalent. Is it so ?

Suppose we have two spaceships a lightminute apart from each other. Ship A sends a photon to ship B. To my knowledge the photon will arrive at ship B a minute after is was departed from ship A. The photon will travel away from ship A with speed c, and will travel towards ship B with speed c...

I am reading MWT gravitation and on page 676, they are talking about orbits of photon, and I don't understand it very well. Energy and angular momentum of the photon are important as a ratio when calculating the orbit. But not energy alone or angular momentum alone. Why is that, and the energy...

Hi, I read the Feynman's book about the quantum electrodynamics and I realized, that he was talking about the different speed of photons. I know, that the light travel's "slower" in a material, but he is also talking about the different speed of photons. I read on the web, that some photons...

The eigen wavelengths λn(WL) of EM radiation in box are 2d/n where d is the size of the box. If I put a photon in a box with WL>2d via an optic cable trough a hole it must reflect on the perfect mirror walls and be a running wave. Maybe it is possible to decompose it as a set of eigenmodes of...

Hello guys. I was thinking about solar sails and was wondering if it was possible to instead simply create a sail that is pushed by photons create something that creates an opposite force that pushes off the photons. If you did this in theory would you not be able to double the momentum? An...

I think that if we plot an inertial frame in the XY axis separated 90º, the photon, which has a velocity of c, should be put on one of the branches of the light cone. The questions are: Which branch, left or right one? Which position along the branch, if I don't know the distance it has...

Be the red point this spacecraft , the purple line the world line with slope = 2 and the green point a photon thrown towards the Earth from the spacecraft , would this spacetime diagram ok? (distance would be 1.2 billion km, and the time, 1000 times of shown, but scale is badly displayed, even...

In Griffiths Elementary Particles (2nd, revised edition) there is a footnote on page 241, which states that the photon states with ##m_s = \pm 1## are related to the polarization vector by: $$\epsilon_+ = \frac 1 {\sqrt 2} (-1, -i, 0) \ \text{and} \ \epsilon_- = \frac 1 {\sqrt 2} (1, -i, 0)$$...

Why photon interact weakly with their environment over long distances ?

I just want to confirm something. You need about 13.6 eV of energy to ionize a hydrogen atom in the ground state. Can the atom absorb a photon with 15 eV of energy? I think it can. This would free the electron, and the freed electron would move off with a kinetic energy of 15 minus 13.6 eV...

When light travels through a medium like water, it slows down and its speed is no longer equal to c. How does this affect the life time of the photon?

We're told that single photons passing through a double slit produce an interference pattern, but the act of observing which slit the photon passes through causes the interference pattern to show a simple ballistic pattern instead. But observing which slit the photon passes through necessitates...