The photon is the quantum of the electromagnetic four-potential, and therefore the massless bosonic particle associated with the electromagnetic force, commonly also called the "particle of light". Use this tag for questions about the quantum-mechanical understanding of light and/or electromagnetic ...

learn more… | top users | synonyms (1)

0
votes
0answers
15 views

How could you slow down or change direction with photonic propulsion?

So you have a laser shooting at a sort of solar sail to transfer momentum in the forward direction but could you have an onboard laser and turn the laser around to hit another sail? How could you turn ...
0
votes
0answers
20 views

Calculating saturation current and energy associated with a band of wavelengths

Consider white light whose wavelength spread is from 400nm to 700nm. Its energy is uniformly distributed in this spectrum. The light is incident on metal A of work function 1.55eV. Saturation ...
1
vote
3answers
112 views

Does an electromagnetic wave necessarily contain many photons? [duplicate]

I've often come across people saying from a quantum physics standpoint that an electromagnetic wave necessarily contains many photons. But doesn't the double-slit experiment conducted one photon at-a-...
0
votes
1answer
44 views

What determines the color of photon that is emitted from an exited atom?

I understand the principle of how light is emitted from an atom. What I don't know is why neon atom is red and copper is green when exited? Is is the distance between the electron to protons or the ...
0
votes
0answers
23 views

Pair production in different reference frames

I understand that energy of photons is defined by their wavelength/frequency. This frequency (and so energy) will be different for different observers: observer moving towards the photon will see ...
1
vote
0answers
56 views

Does a photon follow a straight trajectory in a thin transparent film? [closed]

Emulsion films (developed by F.Powell) /by example/ show that elementary particles follow a straight trajectory staying in a film. The reason was clarified by Francis Mott in his famous 1929 paper ...
0
votes
1answer
25 views

Is linear polarization of entangle photons in 2-particle decay always correlated?

In Aspect's paper "Bell's Theorem: The naive..." and in an 2002 AJP article by Dehlinger and Mitchell "Entangled photon apparatus..." the photons are described to be in the $|xx\rangle+|yy\rangle$ ...
0
votes
1answer
60 views

Coulomb law and photons

When we consider process like $e^- e^- \to e^- e^-$ in QED, we see that from exchanges of one photon (tree-level diagrams) one can obtain Coulomb's law, while loop-diagrams give quantum corrections ...
3
votes
1answer
59 views

Why do some elements burn different colors? [duplicate]

I have a torch lighter and it makes a green color when the flame passes over the metal in the center. What on the molecular level would a flame change color although there is no difference in ...
4
votes
3answers
130 views

Why can't incoherent light be collimated as well as laser light (e.g. in a laser pointer)?

Why does a laser pointer contain a laser diode, and not just an LED? A laser pointer contains a laser diode, which essentially shines coherent light over a large angle, and a collimating lens, to ...
0
votes
3answers
103 views

Is this true about low-light/one photon at-a-time double-slit interference?

I've consistently noticed in pictures of double-slit interference when very low-light or one photon at-a-time is used, that there's lots of "stray" photons detected in the areas of destructive ...
1
vote
0answers
20 views

Time Dilation for a photon [duplicate]

Does a photon experience any time. Since a photon is massless and hence travels at (c) then it should suffer infinite time dilation, and hence shouldn't experience no time?
23
votes
1answer
859 views

How can my window not scramble the image of my yard?

How can an image pass through a window if the atoms in the glass randomly emit photons in any direction? I've read that glass is transparent because the atoms don't readily adsorb visible light, so it ...
-2
votes
1answer
127 views

How far does a photon move in the 4th dimension when it travels one light second? [closed]

In one second a photon moves 3x10^8 meters through the three spatial dimensions. Light's velocity is 3x10^8 m/s. If the photon moved at all in the fourth dimension, it's velocity would no longer be ...
0
votes
0answers
20 views

Mirror shake emulation for the light

Is there any way to simulate mirror shaking? Final goal is to make send light beam to the mirror and get reflected beam the same, as it happens if mirror is vibrating. Mechanical vibration is limited ...
4
votes
0answers
25 views

Relationship between oscillator strength and cross section

In the context of absorption of photons by atoms, I have come across two seemingly very related quantities, cross section and oscillator strength. In the book Physics of the Interstellar and ...
4
votes
3answers
80 views

Where does the energy of a photon trying to escape a black hole go?

I've heard "light cannot escape a black hole" explained several ways. One is that if a photon inside the event horizon tries to escape a black hole it loses energy to gravity. As it loses energy its ...
0
votes
1answer
23 views

How to get explicit value of Wigner angle for massless one-particle state transformation?

The one-particle massless state $|\mathbf p , \sigma\rangle$ is transformed under the Lorentz group $U(\Lambda) \equiv U(\Lambda , 0)$ as $$ U(\Lambda)|\mathbf p, \sigma \rangle = \sqrt{\frac{(\Lambda ...
4
votes
1answer
50 views

What is the QED model about half wave plate?

Surely classical electrodynamics (CED) has a good and well-known answer about the change of light polarization in a HWP (or Quarter wave plate). I tried to find how does this look like from point of ...
1
vote
0answers
44 views

Can 2 photons make up the same colour as another photon?

So, my question deals with the excited electron shown above. (1st diagram) This electron can return to its ground state by either of two ways. One of the ways involves the emission of 2 photons. (2nd ...
0
votes
0answers
22 views

breaking bonds with light

Light, for instance green light (532 nm = 2.33 eV) has an energy comparable to that of many chemical bonds (C-C bond dissociation energy is about 3.6-3.7 eV). So how is it that I'm not being burned ...
0
votes
0answers
77 views

What is a soft photon?

I accidentally came across the words "soft photon" today after reading a few blogs. There was some discussion of special situations involving gauge redundancies and a theorem by Weinberg. What is a ...
29
votes
4answers
5k views

Why have our eyes not evolved to see “gluons”? [closed]

Bit of a random question...photons are the propagators for QED, and we rely on photons to see the world around us. The gluon is the propagator in QCD. Why have our eyes not evolved to see gluons (...
0
votes
0answers
28 views

Photoelectric effect vs. electronegativity?

What connection exists between the photoelectric effect and the electronegativity of a material struck by light? I'm summing up some stuff in physics, and I got the feeling that the amount of energy (...
0
votes
3answers
58 views

The principle behind Inertia and it's connection to Equilibrium

Inertia is the tendency of a force-free body to remain in that state or it is something that opposes any act of changing its equilibrium state. Mass is a measure of inertia. I have some questions ...
1
vote
0answers
36 views

How Does Silicon Surface Barrier (SSB) radiation detectors work?

I'm dealing whith some old detectors (about 1980) called Silicon Surface Barrier, searching online I've seen that they consist on metal-semiconductor(Si n-type) junction (schottky diode) and in one ...
0
votes
0answers
27 views

How can absorbtion of a photon in an atom take place? [duplicate]

I will come back to a question posed here and the comment given by John Rennie: If the photon energy doesn't match an allowed transition energy it won't be absorbed and won't excite any transition. ...
0
votes
1answer
27 views

The highest photon energy ever measured and transplanckian energies

What is the highest energy of we have measured of a photon by any physical experiment? Has a transplanckian energy photon been measured? Can we study them -if they exist- with special relativity?
-1
votes
3answers
72 views

Mass and frequency of photons [duplicate]

Light is affected by gravity which means light has got mass. Quantum theory tells us that light consists of discrete quanta of energy, which we call photons. These photons have a rest mass of zero (as ...
2
votes
1answer
23 views

Point source of monochromatic photons - self-contradictory in QM?

Suppose we have a point source of photons located somewhere in space. So when the photons are released their location is well known, $\Delta x \approx 0, \Delta y \approx 0, \Delta z \approx 0$ ...
1
vote
1answer
27 views

What determines photoelectric yield

Is there any difference between the photoelectric yield of different metals apart from the threshold wavelength? To be more clear: Will metals with the same work function emit the same amount of ...
1
vote
2answers
75 views

How do single photons travel from here to there

I know there have been similar questions but I'm still unclear what the overall consensus is. (1) I assumed and have read that photons travel in straight lines unless deflected by gravity but there ...
0
votes
0answers
29 views

Estimating “attributes” of a single photoelectric interaction

Disclaimer: I'm a mathematics grad student working on medical imaging. My knowledge of physics and physical intuition is, for the most part, quite poor. Question: I've been reading a lot about the ...
1
vote
1answer
101 views

Does this length refer to wavelength or length? [closed]

In this question: A He-Ne laser emits red light of the wave length $\lambda = 632.8\ \mathrm{nm}$ with a beam diameter of $2.0\ \mathrm{mm}$ and a power output of $1.0\ \mathrm{mW}$ [...] (d) How ...
0
votes
0answers
29 views

How can air pollution contribute towards light pollution?

I was just wondering if air pollutants such as soot, could reflect light into the night sky, and thus be a potential source of light pollution. If that's true, can you please suggest any other air ...
7
votes
2answers
174 views

The lightest photon ever detected

Wiki says that a photon of mass equivalent to $10^{-62}$ kg has been detected: 10×10−62 kg Mass equivalent of the energy of the lightest photon detected [citation needed] this equates to a ...
3
votes
2answers
41 views

Is the electromagnetic spectrum bounded somehow? [duplicate]

Is there a maximum frequency that an electromagnetic wave can support?
1
vote
2answers
61 views

Description of a photon and quanta

Could someone please help to clarify the difference between a photon and a quanta? Below is my current understanding - please correct me if I am wrong. A photon - is a 'wave particle' of 'light'. I ...
0
votes
0answers
52 views

Why call it a particle and not a wave pulse?

My physics textbook says that photoelectric emission provides conclusive evidence for the particle theory of light. Apparently, since photoelectric emission only works at certain frequencies, we can ...
0
votes
0answers
44 views

Equation for Electric and Magnetic field from the equation for a “massive photon”

I was reading the Quantum Field Theory book by Maggiore. There he says that in side a superconductor the photon satisfies the equation $$(\Box+m^2)A_\mu=0$$ Then he adds that the electric field and ...
3
votes
1answer
32 views

DNA breaks with particles or photons (Radiation therapy)

When protons (or other particles) or photons are used in radiation therapy to treat cancer patients, the main effect is for it to make DNA breaks that hopefully will make the cancer cell die ...
0
votes
1answer
53 views

Does slowing light violate relativity?

Last year Scottish scientists managed to slow down photons in vacuum by changing their shape. Does this violate the special theory of relativity?
0
votes
0answers
26 views

Which information is lost, if we model photons via the Klein-Gordon equation?

The Klein-Gordon equation describes relativistic spin-0 particles. Each component of the Dirac equation fulfils the K-G equation, c.f. here. If one decides (for whatever reasons) to model photons via ...
0
votes
1answer
64 views

How do photons interact with nucleons [closed]

Is question can be considered as an extension of the interaction between photon and atomic electron, where the energy level of atomic electron is elevated when absorbing photons and the process is ...
0
votes
1answer
68 views

Is it possible to strip the magnetic, or electric field from a photon?

A photon is made up of a magnetic part and an electric part, but we can see the existence of these fields without the other one so I would like to know if it is possible to somehow separate one field ...
0
votes
0answers
20 views

Why triplet-triplet annihilation requires less power than two-photon absorption?

Both two-photon absorption upconversion (TPA-UC) and triplet-triplet annihilation upconversion (TTA-UC) have quadratic dependence on incident light intensity (ref): TPA requires two simultaneous ...
2
votes
1answer
121 views

Continuous X-Ray spectrum

I'm reading Eisberg's Quantum Physics book and came across the following graph I know very little about the subject, but from that figure I understand that, depending on the energy of the incident ...
0
votes
0answers
15 views

Shouldn't HDM drain photons energy?

Hot dark matter (HDM) would be made from very light, fast moving particles. Such particles could not possibly be gravitationally bound to any structure, but rather would be dispersed all across the ...
1
vote
1answer
23 views

When thermal IR gets reflected from an object, does it change its wavelength (frequency)

I'm working with thermal infrared (IR) cameras to detect human thermal radiation. I notice I can easily distinguish non-human objects throughout the camera's field of view, though all are at same room ...
2
votes
1answer
41 views

Number of photons through glass [closed]

I am getting mixed information on the total photon count involved with light transmission through glass. I'm not looking for percentages and I don't have equipment to count photons. For simplicity ...