Photon Definition and 1000 Threads

Hi, I am a new member here. I am a non-physicist. I have been told that the electron is an elementary particle. I have been told that when an electron moves to a lower shell there is a photon emitted. If the electron is elementary where does the photon come from? Thanks in advance for your...

Reading the post below on event horizon of a black hole (BH) got me thinking about the photon sphere of the BH. We all know light will travel around this photon sphere and how light from a source would completely travel back to it's source if one could see it real time, we all know this from...

I am puzzled by that statement. I do not intend to question the statement that "photon doesn't admit to define a position observable". My confusion is with the conclusion that photon is less "classical" because it does not have position observable as I can reach only weaker conclusion that...

Two photons arrive at a hypothetical 50:50 Beam-Splitter with no phase shift between reflected and transmitted modes. One enters the Left side and the other the Bottom side of the BS as shown in Fig.1 of the link below: https://drive.google.com/open?id=0B5JsDLKoUSA5emk5Qk9nUHVIelE Each photon...

I have read that photons do not experience time... If that's the case then if a particular photon is emitted by a body then that should exist in every time relative to us i.e that same photon should be there at exactly the same point forever.

I know that my title is not very suitable for this question, but I couldn't find right words to describe the situation.I read a book called '101 Quantum Questions ' and there writer states that when electron absorbs energy and goes higher energy level, we don't know when and where it will come...

I came across this article on the shape of a photon https://cosmosmagazine.com/physics/what-shape-is-a-photon However, the first image confused me, is it showing the wave function? Most other questions regarding what a photon "looks" like seemed to dismiss the question.

In a 'one photon at a time' double slit experiment, does the interference pattern still emerges if the time delay between individual photon emissions is increased to minutes or even hours?

Is the spin of a photon pointing in the same direction as the magnetic field of the photon?

Dear All, I have a couple questions on the double slit experiment I hope you can help shed some light (or photons) on. =) Arrival Timing of Photons In a normal double-slit experiment like the above setup, do photons always arrive at the detector at a constant speed (basically, speed of light)...

I have read in textbook that if a photon were to collide with a free electron it's an impossible situation for photon to get completely absorbed by an electron . The situation seems possible by conservation of energy but I am not able to understand the true reason behind the statement .is there...

Dear All, I have a question on the double slit experiment. From the references I've read so far, they are focusing on the results of the detector AFTER the 2 slits. Let's say when photons are fired, how many % actually pass through the slits and get detected at the end? Would some (and how...

Homework Statement In-phase light from a laser with an effective power of 2x105J and a wavelength of 1064nm is sent down perpendicular 4km arms of the LIGO detector. (i) Determine the number of photons traveling in the interferometer arms. (ii) Assuming the detector is sensitive enough to...

i found reading the possible interaction of neutrinos with photons to not "level tree", what's the meaning of level tree? and how is that posibble ?

Hi all, This is likely a naive question, following up on something @vanhees71 posted some time ago in another thread: My question is the following - if we take an electron that has, for example, absorbed a photon, is the portion of the wavefunction representing the electron in a lower energy...

What would be the energy (eV) of a gamma ray photon with the wavelength h (Planck's length)?

I need to determine the best boundary shape for tracking photons being emitted from a cesium 137 DISK SOURCE that would be hitting a POINT DETECTOR 50 cm away. The cesium is not contained by anything, it is only traveling through air. What I mean by boundary shape is: the software tracks...

Homework Statement An Fe nucleus (A=57) decays from an excited stated to the ground state by emitting a gamma ray. The energy of the photon is 14.4 KeV when the nucleus is held fixed. If the nucleus is free to recoil then the energy of the photon emitted will be? Homework Equations ## E =...

Homework Statement Consider Compton scattering of a photon by a moving electron. Before the collision the photon has wavelength λ and is moving in the +x-direction, and the electron is moving in the −x-direction with total energy E (including its rest energy mc2). The photon and the electron...

Consider an amplitude for some subprocess involving an off shell external state photon with polarisation ##\epsilon_{\mu}## and momentum ##q_{\mu}##, stripped of the polarisation vectors so that e.g ##T = \epsilon_{\mu} \epsilon_{\nu}^* T^{\mu \nu}## (##\epsilon_{\nu}^*## is polarisation vector...

Gamma rays scatter and ionize atoms, which stretches out their wavelength, right? How many ions could a single gamma ray photon create before it's absorbed due to the photoelectric effect?

Hello, A photon can have various types of polarization states (horizontal, vertical, circular, elliptical, linear at an angle ##\theta##). Any valid polarization basis is two-dimensional and can represent any state of polarization. What are the actual eigenvectors of the polarization...

What is the best way to imagine a photon? Sometimes I hear that they are simply transverse waves with oscillating EM fields, which just move forward. Other times, though, the photon is said to move along the wave. The third image reminds me of a probability wave. So which one is correct...

Hello, I have a presentation tomorrow and in a segment, I talk about light absorption. It's more conceptual than technical. I did quite a bit of research on the topic but because of simplifying information I may have butchered the facts and written something wrong. Could anyone please confirm/...

Homework Statement [/B] The problem is as follows: in a reference frame there is one electron at rest and one incoming positron which annihilates with the electron. The positron energy is E and two gamma rays are produced. Find first the energy of the photons in the center of mass frame as...

Is it possible to associate electric and magnetic fields with the vibrating string that is thought to represent a photon in string theory? Thanks!

If a mode of light is in the single photon state in the reference frame of the emitter, what will the state look like in a reference frame where the wavelength is, say, 5% less or more? How about a state with, say, 5 photons? I saw some online discussions and some papers on arXiv (not...

When I search for "on demand photon pairs" I find that most publications are about entangled pairs. I found no papers and articles about on-demand pairs where the photons are identical in all respects except their direction, and whose polarization & frequency are the same across pairs and...

Hi there, I was wondering what the relationship between the photon and the electromagnetic wave is? Is the photon traveling on that wave like a surfer is riding a wave? :-) Thanks in advance!

Homework Statement So me and my friend were comparing our homework and we noticed that although we had the same answers, we both had different ways of answer them. So I was just wondering who's work, my friend or mine, is the most correct?Here's the questions. 1. Calculate the momentum of a...

Homework Statement Hey everyone, So my teacher assigned a mini project just before our finals and I was wondering if someone could look over my work and my calculations. I just want to make sure I understood everything since my final exams are coming. Here's the assignment. Compare and...

We have studied the weird enough not continuous energy aka photons, And that they are like the way that waves interact with matter by giving them bursts of energy and that these photons have relativistic mass ( Before you give me the FAQ link, I have read it.). Mass is a property of energy. So...

Hello all, I have a question that's been bothering me the last few days and wasn't sure where to turn. Recall the original Special Relativity thought experiment: A spaceship travels at constant velocity v, moving in the positive x direction. An observer on the spaceship emits a photon directly...

Hi, Can someone tell me the reason why it is impossible for the photon to have a rest-mass? Without referring to the theories which are actually build on the fact that the photon is massless. Is there any possibility that the speed of light is not about light and that there is some...

Homework Statement A photon with the length of lambda hits a cathode perpendicularly to its surface. As a result, an electron leaves its surface perpendicularly to the direction of the photon. How much momentum was transferred from the photon to the cathode? The work function of the cathode is...

I just started reading general theory of relativity. I have some elementary questions. Not an english speaker so bear with me. I am reading the thought experiment which describes path of a photon in a free falling lift. For an observer inside the lift, the photon path is a straight line. But...

Black hole or more correctly the event horizon will not let anything past through it, from inside to outside, ok. But then we get to a particle with zero mass eg. photon. How can gravity act on that particle, surely for gravity to act there must be mass? Or does it act on the electromagnetic...

Homework Statement How much work is required to accelerate a proton from rest up to a speed of 0.999c? What would be the momentum of this proton? Homework Equations p=γmv The Attempt at a Solution I got part A, which was the momentum. I found that to be 20.1 GeV. Now for part B I have to find...

Apparently, in QM, the photon does not have a position operator. Why is this so? As usual, thanks in advance.

Hello everybody, I'm playing with a ne -ne laser And i conducted an interesting experiment I did colliding beams the type of interferometer Fabry Pero between the mirrors I put the cuvette with different substances I tried to detect changes of polarization of the laser beam with the help of a...

Consider the double-slit experiment done with photons from a laser. If one was interested only in computing position (vertical) probability amplitudes and did not care about spin/helicity, could the Klein-Gordon Equation (with mass set to zero) be used? Thanks in advance.

It occurs to me that I've probably been confusing "phase" in a number of contexts. In particular: 1) If we write a photon's polarization as \psi = |x\rangle + e^{i\theta}|y\rangle, then we can call \theta a "phase." 2) When a photon bounces off a mirror, it picks up a relative phase of i. If I...

If a Z can decay to a photon, what happens to the Z's weak charge?

Is it possible for a photon to be so energetic that it forms a black hole? If so, how fast would that black hole be moving?

In a nutshell, does Newton's "action = -reaction" law apply to massless particles? If a spaceship directs a condensed light beam on its own heat-resistant photon sail, what would happen?

@phinds noted in a recent thread that energy is not conserved on a cosmological scale, which hadn't occurred to me before, so I did some reading and happily the concepts were easy to digest and things I already understood but just hadn't connected the dots myself on regarding the implications...

Hi! Could someone explain to me why an electron at rest without any influence from a magnetic or electric field cannot emit a photon ? Could you explain it mathematically too ? Thanks in advance...

Wikipedia(https://en.m.wikipedia.org/wiki/Photon_sphere): 'This equation entails that photon spheres can only exist in the space surrounding an extremely compact object (a black hole or possibly a neutron star)' But how can a neutron star? I have a doubt because 1. When а mass of а star...

Hello! I have a question about the photon propagator in Feynman diagrams. I am looking over a brief derivation (probably there are some details missing), so basically it starts from Proca equation for a mass 0 particle, then it assumes Lorentz condition and in the end it obtains...

Hello! I am a bit confused about the completeness relation for photon polarization. So it says ## \sum_{s=1,2}\epsilon_i^s\epsilon_j^{s*}=\delta_{ij}-p_ip_j##, with ##p_i, p_j## - unit vectors. So I am not sure what are the indices i and j. I though that they represent the component of the...