Photons Definition and 1000 Threads

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...

These articles have energy but do they have mass?

Suppose a atom has two energy levels ##\hbar \omega _ a##, and ##\hbar \omega _b##, and let ##\hbar \omega _0 =\hbar \omega _b -\hbar \omega _a ##. Also, there is a phton with enerigy of ##\hbar \omega##. If ##\hbar \omega =\hbar \omega _0##, then a atom in level ##\hbar \omega _ a## can absorb...

Let's assume the following sine signal sent by a low frequency (100 kHz) transmitter. I think with the information that the sending power is 1 watt and the starting phase is 0 the signal is fully described. Are the following assumptions correct?: 1. The frequency of all photons leaving the...

Assumption: Screen detector is much closer to the slits than in "standard experiment" and the small angle approximation can't be used to determine the interference fringe maxima, but the interference pattern still occurs. Is it possible to measure the time of detection in such setup accurately...

This above is the diagram I'm not too sure about the solution to this problem as to why I came here. Is it something to do with photons having different frequencies i.e emitting different amounts of energy based on its frequency

The following is a diagram of an EPR thought experiment using photons that uses the same type of components as described in this paper http://www2.optics.rochester.edu/~stroud/cqi/rochester/UR19.pdf Would you detect any photons at the right detector? I want to be convinced one way or another...

Do photons, I'm not sure how to express this, "experience" time? Since they move at the speed of light does time not exist for them? If time does not exist, how is it possible for anything to happen to them. If interacting with matter requires a change in their condition, how can a change in...

P.t = nhf n/t = P/(hf) = 1.25 × 10^16 Something wrong with my working or I just pick (E) as answer? Thanks

Hi all, I've been wondering: Thinking of Arthur Eddington's relativistic oriented 1919 eclipse observation, would the photon deviation due to the Sun's gravitational imposition have caused the photons to exhibit a qualitative redshift due to the time photons had spent within the Sun's...

I think since Esystem=(PsystemC)^2 + (Minvariant C^2)^2. Then the invariant mass of the system should be zero, but I am hesitated with this is it always the case that photon that travels perpendicular to each other have zero invariant mass

I've tried using gammamc^{2} = E1 + E2 but how do i find gamma?? If i try to use the kinetic energy then I just get gammamv^2 = 1gev but i don't know v? very confused

I've been trying to generate entangled photons using KTP laser pointer that normally produces green light at 532 nm. I was hoping that after removing the IR filter, I could add a reflective coating (right now the coating I have is a glittery metallic green nail polish) to reflect the green light...

In A.P. French's Special Relativity, the author said the following, As I understand, photons are massless, so I don't think the last equation above applies to photons, but then, when deriving it, he used an equation proper to photons (##E=pc##). So in which context is ##m=p/c## valid?

Few days back, our college professor told us that if a photon were to have a finite mass, then the Coulomb potential between two stationary charges separated by a distance r would be strictly zero beyond some distance. He told us that it was due to the reason that photon is the elementary...

Hi PF i am reading a book written by L Tarassov about the Young slits experiment there is a source of photons in the middle behind the slits. when the electron passes thru one slit the photon is detected by a camera near this slit or another near the other slit. there is a probablité thar the...

According to the 2nd postulate of Special Relativity, speed of light in vacuum is the same in all inertial reference frames. If I take a beam of photons and see the other photons in the beam from a frame of reference of a single photon, do they look stationary or moving at the speed of light...

If the light slows at an interface, what happens to the photons coming in after the slowed ones? Can these cohere with the leading (slowed) ones and create what amounts to a FEL?

in the inside of the material is heat also can transferred by radiation?

Summary:: need to increase the wavelength of light. I am an intro physics student working on a project and need to increase the wavelength of photons. I only have visible light sources available but need to have an emission of a wavelength larger than 1mm. is there a way to shift wavelength...

Once I have read that we can’t know a actual position of a particle because to see the particle we need to send photons and when we send photons it colides with the particle and change it’s position. Is this true?

In quantum electrodynamics, the energy exchange between two charged particles is called a virtual photon, allowing the exchange of quanta of energy between the two charged particles. But these are not the traditional photons of electromagnetic waves. They apparently just arise from the equations...

After emitting two photons (or any other kind of energy) in the direction of motion and in the opposite direction, the velocity of the body (a big charged and unstable particle) remains unchanged, while the kinetic energy decreases. This entails a decrement of the rest mass, or of the inertia of...

Let me clarify this by a thought experiment: Imagine, a heated, red-hot (emitting only monochromatic red light) metal bar is brought inside a dark room. The room is practically insulated and the metal bar is glowing in the dark - emitting 'red photons' of visible light. Eventually, the bar...

According to QED photons can be absorbed or emitted by electrons, and this process results in em forces via virtual photons. What determines the emitted photon frequency, and are they fully absorbed by electrons assuming photons are discrete and must be in quantized packets? How fast are...

It has been reported [http://www.astro.yale.edu/larson/papers/SciAm04.pdf, https://www.scientificamerican.com/article/the-first-stars-in-the-un/] that scientists have observed spectra of radiation emitted by quasars that date from about 900 million years after the big bang. Others have observed...

My question comes from reading the wikipedia page on mass-energy equivalence. The statement would seem to be contradictory: So photons contribute to the energy (and therefore mass) of the container; but photons are massless - that is, they have 0 rest mass. But doesn't this mean that we're...

According to this link photons can interact with each other through the creation of other particles. My questions are do they have to have the same wavelength to be able to interact with one another? Is there a threshold where they start to interact with each other?

The following extraordinary experiment from Caltech highlights the 'classical' behaviour of light(photons) traveling through medium. It vindicates the notion that photons(at least from our limiting human perspective) do behave the same way as other quanta(much like ordinary 'matter' - chairs...

In the double-slit experiment, is there experimental evidence that a photon detected passing a slit always results in one and one only screen point?.

This is the phenomenon of a photon simultaneously exist in many different spaces, experiment show that space does not exist and the distance is not real. This experiment bring a lot of sense in quantum research. I want to review again but forgotten the name of person that did it.

I came across a question recently which involved calculating the change in wavelength of a photon between being emitted from the surface of the sun and arriving at the Earth. The method that was implied involved calculating the GPE's of the photon (assuming the photon to have a mass h/[c...

Why do photons only interact with charged particles?

Hi, I am aware that the reason why objects have color is an old subject. However I come across two claims which sound like they are in contrast to each other. On one hand I read that the photons with specific frequency in incoming light are absorbed (i.e. have enough energy to move an electron...

As the thread on Jürg Fröhlich's paper on the "ETH interpretation" of QM has been closed, I want to consider here a specific point. Fröhlich points out that this interpretation requires the inclusion of massless particles and I think this is the key to getting a physical understanding...

Are photons vibration or is vibration the transport medium for light? In what kind of medium are photons more transferrable?

This is based on "Concept Question 10.4" in Andrew Hamilton's General Relativity, Black Holes, and Cosmology. I have modified the question somewhat in order to focus on what seem to me to be the key issues. Suppose we have a spherically symmetric ball of stress-energy surrounded by vacuum. More...

Suppose one measures the position of a photon without destroying it. From my understanding, the wavefunction of the photon should collapse, and will return to a more spread out state over time. How would one calculate this, specifically the rate at which the wavefunction spreads out from the center?

Just wondering... If photons do not have a position operator - is it because theory math does not provide it, or because theory math forbids it? - how is speed (the difference between two positions divided by time) determined? - are emission and absorption inferred from measuring energy...

Suppose a black hole with a radius equal to the radius of the observable universe exists and a fleet of coasting spacecraft are moving directly away from the black hole (along a similar vector) at very close to the speed of light with an amount of kinetic energy A with respect to the...

I've read (in Hagai Netzer's book The Physics and Evolution of Active Galactic Nuclei) that "Comptonization in the [black hole's accretion] disk atmosphere can increase the energy of some photons..." I thought Compton scattering could only decrease a photon's energy. What am I missing?

I'm not an expert in this matter, and at best only aware of some superficial facts and a layman's understanding of them. So please forgive me for any ignorant mistakes in my thoughts, and kindly point them out to me. Going by the Lambda-CDM model, the expansion of the Universe will eventually...

Summary: massless particles (or at least photons) are attracted to other photons and to matter, but which is most attractive, and why ... Summary: massless particles (or at least photons) are attracted to other photons and to matter, but which is most attractive, and why ... I am really...

Summary: The limitations of engagement and possible results of the Breit-Wheeler theory collider in relation. *You will need to read the article for this to make sense Upon reading an article "Scientists discover how to turn light into matter after 80-year quest" I had a thought, How will...

Personally, I have trouble visualizing a flock of birds without the birds. I have the same trouble trying to visualize an EM field without the photons. More than once, I have been hounded off of the ham radio forums for mentioning the word "photon". As one ham radio operator put it, "We don't...

we know that when a electron lost its energy , it will emit photon , but why electron have a photon inside ? does it already exit in a electron from the beginning or it comes from environment ? if comes from environment , where does photon come from?

It would seem that they both must observe the laws of General Relativity.

How precise can a wavelength of photons be measured and how much can it vary? For example, 300nm, 300.1nm, 300,11nm, 300.111 etc... What is the limit up to which we can measure it or is there a point where there is no variation anymore - something like a "quantum" of wavelength? Hope you...

Photons deviate from the above energy-momentum transformations under certain circumstances while still in flat space-time, I'm wondering what set of transformations would more accurately describe them over as wide a range of circumstances as possible, still in flat space-time, I've searched and...

Hello, I have some trouble understanding how to construct the matrix for the beam splitter (in a Mach-Zehnder interferometer). I started with deciding my input and output states for the photon. I then use Borns rule, which I have attached below: To get the following for the state space...