Photon Definition and 1000 Threads

Hi. I'm learning the optical photon quantum computer from Nielsen's QCQI. Since I'm not familiar with quantum optics, I got some questions about it.Q1. In page 288, the book reads: A laser outputs a state known as a coherent state ##\left | \alpha \right > = e^{- \left | \alpha \right | ^2 /2 }...

Suppose there is a photon with momtum p=h/lambda moving in the positive x-direction. Suppose it collides with an electron at rest and is completely absorbed by the electron, and that after the collision, the electron moves to the right with the same momentum of the photon. This seems...

I'm not that familiar with the current theoretical standing on how electrons "absorb" photons, as in the sense that electrons in an atom absorb photons and move from lower to higher energy states. But during the absorption of a photon the electron, if you set units of c=1, gains energy and...

I'm curious if someone help me understand why the electric and magnetic forces are IN PHASE at right angles to one another? Should they not be 90 degrees out of phase in order to conserve energy? I do understand they are in phase but why? Thank you all for your time. Merlyn.

I've been watching a lot of physics videos lately and a couple of said that photons are massless. What I don't understand is how a massless photon can impart force? Like the ideas of having a laser propel a deep space probe.

I’m watching TV. An excited electron in an LED in the screen falls back to its normal energy state, releasing a quantum of electromagnetic energy in the form of a photon. Let’s call this event ‘A’ (x1, y1, z1, t1). The wave packet of this photon fills the universe (quantum mechanics). Across the...

I've been troubled by this problem for some time now and have received several answers to it none of which I find compelling, so I am posing it again in hopes of getting something more convincing. Here's the problem. Consider one had a large optical interferometer with two siderostats place...

Is it known how much momentum a photon possesses if it's wavelength is at the Planck length, and what happens if it's momentum is somehow increased from that?

So a photon is absorbed into and emitted from electrons, causing the electrons to jump energy levels around an atomic nucleus. And enough energy absorbed into the electron will cause the electron to break from the atom altogether. My question is, where does this energy that enters the...

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A photon with enough energy can create a pair of electron and positron and we call it pair production. And a position and electron meet can create a photon , we call it annihilation of electron and positron. And we know a photon has a spin of 1, when pair production happen , require positron and...

Concrete for example - you need less concrete to obtain the same lead equivalent for photon energy 500 keV than for 200 keV. What is the reason for this?

So I'm a chemistry student here in the UK - and I'm feeling a bit like a fish out of water on a physics forum but... I'm having trouble with a derivation that seems simple but i can't for some reason seem to understand. I know that the energy of a photon is given by E=hc and that c=lambda*v...

Is a photon simply a propagating vibration of the spacetime lattice similar to gravitational waves but at a different wavelength and amplitude, and the electron that creates it plucks a single lattice string rather than a bunch? Therefore it has no mass and travels differently through spacetime...

Consider a mass in its restframe relative to which another mass can have an arbitrary velocity ##v < c##. Now consider a photon in its hypothetical restframe. Can a mass have an arbitrary velocity ##v < c## relative to the photon?

[Moderator's note: This thread has been separated out from the FAQ entry since questions or suggestions about FAQ entries should not be cluttering up the FAQ entries themselves.] I would like to suggest that it might be more proper to base the "rest frame of a photon" theory explanation...

Now...exactly when and how do CMB photons lose their 3000˚ K creation energy to become 2.7˚ K?

where is photon located when it is not absorbed by electron? Magnetic field?

Hello everybody, In this Wikipedia article we find an equation for a photon gas which contradicts an equation given by Stefan Weinberg in his book "The first three minutes": https://en.wikipedia.org/wiki/Photon_gas The equation given here has 16 π k^3 ζ(3) T^3 in the numerator and c^3 h^3...

How is a Photon being created?I mean not light but photon? Is it created by atom when it realeasing it energy ?

Would it be possible for photons to form some sort of static structure, like a standing waveform, if space-time was curved enough? It seems like a structure like this exists around black holes. Is there any other distortion or phenomenon that could cause this, such as a neutron star or a galaxy?

My personal course of study in quantum mechanics hasn't brought me this far and so this question may be incredibly naive, but it has still been troubling me. If the energy of a photon is E = (hbar)(omega) and the units of hbar are J*s (obviously), then how can a photon have no mass if a J is...

The other day I was playing my favorite time waster (World of Warcraft), and someone started to talk about flat earthers. I thought of stirring world chat a little bit, so I posted that while the flat earthers were a lot of odd folks, one could argue that for a photon the Earth indeed looks...

Has anyone ever tried to measure the number of waves in photon wave packets? It seems like that would be an important feature and would be equal to the number of fringes in the double slit experiment (on one side), unless it is a huge number. Also, the decrease in the intensity of fringes as...

Long time reader, first time posting here in physics forums. I know that according to relativity photons have no proper time. I also know that a photon of sufficient energy can interact with a nucleus's nuclear force via the weak interaction resulting in pair production. I was looking at a...

Homework Statement Hello, I am currently working on photon diffusion equation and trying to do it without using Monte Carlo technique. Homework Equations Starting equation integrated over t: int(c*exp(-r^2/(4*D*c*t)-a*c*t)/(4*Pi*D*c*t)^(3/2), t = 0 .. infinity) (1) Result...

This might sound stupid , but I am wondering how exactly could I describe the momentum eigenfunctions of photons? EDIT: to destroy ambiguity, I am searching for a quantum mechanic description of monochromatic light similar to how we represent it classically as: E-> = a->cos(wt+phi)

I'm interested in knowing the ratio of momentum for a neutrino vs. a photon when both have the same energy. Alternatively, my spaceship engine can release 1GW of either a photon beam or a neutrino beam. How much relative thrust will the neutrino beam give me for the same energy (and power) as...

I understand how polarization can be explained using EM waves. However, I am unable to understand how to explain how polarization filters work when we use the concept of photon spins. Can someone help me with that?

Why did the expansion of the universe cause an increase in the wavelength of the photons that existed during the time of Photon decoupling ? Does this mean that expansion of universe stretches everything and stars that were present when the universe considerably expanded also got stretched?

If you had a universe that only contained a single photon - would it be valid to call it a universe? If so, what properties would it have, like time, no of dimensions etc? And if you added a second photon,could you say that you then have a universe with 2 photons in it?

Everyone knows that matter and antimatter annihilate upon contact. But exactly WHY this should happen is not at all obvious, at least to me. So what exactly happens when two such particles encounter one another that leads them to disappear in a large release of photons? And for that matter...

Homework Statement Using quantum mechanics, what happens when a photon of light hits glass? Homework Equations Momentum= Mass x velocity The Attempt at a Solution I am not sure of my answer but suffice to say the following: Assuming the collision between the photon particle and those in the...

Is there any way to accurately measure the wavelength of a single, individual photon? How precise could such a measurement be? I will be satisfied if the "measurement" consists only of confirmation that a photon from a monochromatic source has the expected value, as long as it has sufficient...

I am working on a problem determining dose rate using MCNP6. I am following two papers that did the same type of simulation and in them they multiply the tally results by the photon yield also called the photon intensity to detrime the dose rate. My question is where does one find this value ...

Ok so I drew up something (I know its horrible), but is this correct? Does the black line in the middle represent the propagation of the photon? If this is correct I would like to know and anything else that could help me or just anything related to this.

Let us assume that we have a large gravitational field, then the gravitational redshift can be expressed as, $$\frac {v_{\infty}} {v_e} = (1-r_s/R_e)^{1/2}$$ In this equation ##v_{\infty}## represents the frequency of the light measured by an observer at infinity, ##v_e## is the frequency of...

Does a photon have mass?

I read that electromagnetic radiation behaves both as particle and as wave, in what is called wave–particle duality. Given that the radio waves of VHF television have wavelengths from one to ten meters, what is the size of a "VHF photon"?

I was thinking a group of photons traveling in a beam of light would create some gravity and attract to each other. But the field of gravity wouldn't be strong enough to affect each other unless it was a high energy group of photons. Is it possible for photons to want to stay together using...

Can we could interfere electron with photon, this question is come from logic both are waves. Is anyone did that before.?(I know that electron isn't a scalar wave)

Does a single photon travel in two different waves at once? If photons are particles like the Photoelectric Effect, Compton Scattering, and Blackbody radiation all suggest, how do polarizing filters block light completely? Is a particle from a radio antenna actually that large in size?

For a photon passing close to the Sun, Newtonian physics predicts a deflection of 0.85o. GR gives the correct 1.7o. Can the true value alternatively be obtained via 1) a Newtonian model, and 2) gravitational time dilation: the photon's slower speed near the Sun leads to it spending more time in...

My experiment is to place a detector on one of the slits in the dual slit experiment so That it would record or not the passage of the photon, and then reset the detector to its base state, Erasing the result. In such a case, would the interference pattern be destroyed simply because the...

for example, when does an electron repel another electron with an electromagnetic disturbance?

Homework Statement Homework Equations (1) E2 = p2c2 + m02c4 (2) E = γm0c2 (3) E = Eγ1 - Eγ2 (4) p = E / c (5) E = hf (6) λ = c / f The Attempt at a Solution a) Using eqn (1), rearranged p = (E - m0c2) / c , I obtained 2.9 MeV c-1. Not sure if I have the right answer here as I...

Suppose you have a pair of electrons in the same quantum state, and are thus spin entangled, and they absorb a pair of photons and release them at the same time. How would this affect the photons? Would the photons be entangled? Would it affect the photon spin, and if so, how would it affect the...

Homework Statement [/B] I have solve the rest of this problem pretty easily and see no problems with working with Indistinguishable particles, Distinguishable particles, fermions and Bosons. Part c has me very confused though about what it is even asking. Suppose a system with equally spaced...

Hey guys, new here. Here is my first question for the forums: Let's say that I have a controlled environment for an experiment whereby I want to heat, say, one cubic centimeter of steel until it is white hot. Assuming that I have perfect containment set up for it such that no energy can be...

Hi, I'm sorry if this question has already been answered somewhere and I'm just too incompetent to find it, buuut: As the title already says, I really do not get that part of quantum physics (if you can even say I'm getting ANY part at all...). As I searched all Google for an answer I just...