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
1answer
25 views

Direct bandgap semiconductor reaction to heat. Produce light?

In an indirect bandgap semiconductor if you apply heat the number of free electrons increases, conductivity increases, and the bandgap decreases. In a direct bandgap semiconductor is there any ...
0
votes
1answer
89 views

What is the bigger number of particles crossing an area: the number of photons or the number of neutrinos? [closed]

Take an squared area with (10²)² m² in front of the sun. What is the bigger number of particles crossing an area: the number of photons or the number of neutrinos? Just for clarification: you can ...
0
votes
1answer
45 views

Does the frequency of photons decrease at outer radii of a helical mode?

A helical mode is a mode of the electromagnetic field in which the wavefront is characterized by one or more helixes. Along the direction of travel, at the center, lies an "optical vortex." The ...
0
votes
2answers
85 views

Photoelectric effect and energy of light

I have a doubt about photoelectric effect and the nature of light in general. From what I understood, in order to ionize a piece of some material, I need an electromagnetic wave with a frequence ...
1
vote
1answer
64 views

Why is blue darker than yellow in an analog black and white photograph?

Blue is perceived darker than yellow by the human eye, because of biological principles within the eye. I can understand that therefore, when making a picture black&white in software like Adobe ...
1
vote
1answer
47 views

Quantum entanglement and Compton Effect

Suppose we generate 2 entangled photons (via a beam-splitter or similar apparatus). They have an arbitrary indeterminate initial frequency $\nu_i$. One of these photons is allowed to propagate through ...
0
votes
0answers
32 views

Do copropagating photon pairs exist?

Countepropagating photon pairs with opposing spin are well known. Are there physical phenomena that produce copropagating photon pairs with opposing spin? Wild speculation: A cooper pair of ...
3
votes
2answers
293 views

Will high amplitude, low frequency light be capable of wrapping around a macroscopic object? [duplicate]

To me, as a macroscopic observer of light, it appears that light moves in straight lines. If I shine a light at object A and object B moves between me and object A, the light hits, i.e. gets blocked ...
0
votes
0answers
41 views

EM wave frequency and photon energy

We know that a quanta of light of frequency f has energy hf. But when I consider a single photon there is no concept of "frequency of a wave" because there is no EM wave associated with it which would'...
1
vote
1answer
34 views

Can we use a photon to use it as a changing field in an electric generator? [closed]

In an electric generator we use a changing magnetic field to create electricity. But what if we use a photon's oscillation of EM waves to generate electricity in a metal wire as we do in an electric ...
2
votes
0answers
53 views

The properties of light photons [duplicate]

Please consider a closed room with light reflecting walls and in the centre of the room there is a Lighting Bulb. Now if I switch on the bulb, the room is obviously illuminated with light. When I ...
1
vote
0answers
75 views

How do I derive Feynman rules for vectors involving derivatives?

Suppose I have a term in the Lagrangian: $$\cal{L} \equiv (\partial_\mu B^+_\nu) B^{-\mu} A^\nu $$, where $B^\pm$ are charged massive vector particles and $A$ is photon. Now, how can we derive the ...
3
votes
1answer
142 views

How can a photon “stop”? What does its world line look like? [duplicate]

Einstein famously made a thought experiment: what would he see if he sat on a beam of light? His answer was -- it's impossible. Owing to him being a body with mass, he can never ever reach light speed ...
0
votes
1answer
91 views

How does a photon raise the temperature of a gas?

The temperature of a fixed volume of a gas is increased when it interacts with radiation. Why does the temperature increase (i.e. why does the velocity of a gas molecule increase) when a photon is ...
0
votes
2answers
50 views

Double slit experiment with a single photon stream

I would like to know if the following are true: Each time you fire a single photon, only one dot appears on the back screen. Is there ever a case that while we are watching the experiment, that a ...
7
votes
3answers
1k views

Is a single photon always circularly polarized?

While trying to understand polarization in quantum field theory, I wondered how a single photon could go through a linear polarizer. I found a paper which asked "Is a single photon always circularly ...
-1
votes
1answer
82 views

What role does wavelength play in the identity of a photon? [duplicate]

According to this question: What determines color -- wavelength or frequency? It is the energy, and thus the frequency of a photon $E=hf$, that determines where it lies in the electromagnetic ...
6
votes
1answer
252 views

How does one account for the momentum of an absorbed photon?

Suppose I have an atom in its ground state $|g⟩$, and it has an excited state $|e⟩$ sitting at an energy $E_a=\hbar\omega_0$ above it. To want to excite the atom, one generally uses a photon of ...
2
votes
1answer
181 views

What is a Lagrangian of a photon? [duplicate]

In sense of classical mechanics+special relativity what is lagrangian of a photon? Lagrangian of a relativistic massive particle is as follows: $$ L_{massive}= -mc\sqrt{c^2-v^2} $$ So is it a zero?
0
votes
1answer
49 views

How does localization affect interferometry?

A classic setup (I suppose it's classic) in introductory quantum mechanics has a single photon passing through a double slitted grating. Directly across each slit of the grating is a device that can ...
0
votes
3answers
150 views

Why can't we see virtual photons? [closed]

If photons are the carriers for the electromagnetic force, then why can we not see electromagnetic fields, given that photons are involved in this interaction?
2
votes
1answer
81 views

Einstein's 1905 “Concerning an Heuristic…emission and transformation of light”

I'm currently attempting to read Einstein's annus mirabilis papers, starting with his introduction of the quantization of light in the paper: "Concerning an Heuristic Points of View Toward the ...
0
votes
0answers
53 views

Inconsistency in illustration of double slit experiment?

So I have 2 questions: 1) In the following drawing, it seems to me that for a concentration spot to show up in the center of the receiver (orange dotted lines), the width of the emitter must be ...
1
vote
1answer
99 views

Uncertainty in the average of a series of photon counting measurements

I'm a bit stuck on a problem relating to statistics in photon counting. I'm measuring a spectra with a spectrometer and can set a measurement time and number of times to repeat the measurement in ...
0
votes
1answer
132 views

how do photons move with respect to EM (I'd like to picture wave magnitudes frame by frame) [duplicate]

(I'm aware treating photon as particle and talking about its position is not exactly, conceptually right but I think it makes sense, at least in the point of view of a beginner. Please just assume ...
1
vote
1answer
31 views

Interpretation of different values of antibunching

When the frequency resolved second order correlation function at zero time delay, $$g^{(2)}(\omega_1, \omega_2) = \frac{\langle a_1^\dagger a_1(t) a_2^\dagger a_2(t)\rangle}{\langle a_1^\dagger a_1(t)\...
0
votes
1answer
41 views

Power and frequency of photons and its relationship with biological safety

I understand that x-rays are more dangerous than radio waves because they are of higher energy, since they have higher frequency. However, it’s less dangerous to stand near a radio station with a ...
0
votes
1answer
46 views

Interactions of light with the air

This is an interesting thought which I had when driving home today looking in my wing mirrors. If you are driving a car and looking in your, say, right wing mirror, you see an image of the car ...
3
votes
2answers
202 views

Why is the Spin of the photon neglected?

We know photons have spin s=1. However, in Nuclear physics, the conservation of angular momentum in case of Gamma transitions is employed as follows: $$\vec J_i=\vec J_f+\vec L$$ where $J_i$ is the ...
1
vote
3answers
141 views

Does orbital angular mometum has no meaning for single photons?

In the quantization of free electromagnetic field, it is found that the left-circularly polarised photons corrsponds to helicity $\vec{S}\cdot\hat p=+\hbar$ and right-circularly polarised photons ...
0
votes
0answers
41 views

High energy photon collapsing into its own black hole

If I did not mess up the math, a photon with a wave length of $$ \lambda = \sqrt{2\pi}\, l_p$$ where $l_p$ is the Planck length has a mass (energy/$c^2$) of $$ m = \sqrt{2\pi}\, m_p$$ where $m_p$ ...
2
votes
4answers
88 views

the relation between frequancy and energy of EM waves

In quantum theory, $$E=\hbar w$$ In classical theory, we have the Poynting vector: $$\vec{S_\space}=\frac{1}{\mu_0}\vec{E_0}\times\vec{B_0}{\cos}^2(kr-wt)$$ given S is energy flux density (the ...
0
votes
2answers
96 views

Velocity of photon when changing direction [duplicate]

We know the speed of a photon is constant. Yet when any other object changes direction, its velocity must go to zero. Thus, my question is how does a photon avoid this? I assume that to change ...
0
votes
2answers
86 views

How energy of a photon or EM wave has something to do with frequency?

While I was thinking what exactly meant by energy in quantum mechanics, I was quite shocked by the fact that it is proportional to frequency. $$E=hf$$ Given the fundamental definition of energy in ...
0
votes
1answer
110 views

Number of photons

When a light source blinks, it "creates" a ball of photons, expanding by speed of light. How many photons are there in one "layer" of the ball (no matter how long is the source active)? Is it a ...
0
votes
1answer
77 views

Why does photon have to travel in sideways to hit the light clock?

From this article, Let’s say Alice is holding a light clock, and Bob is watching her run by, while holding it, with speed V. Alice is standing still (according to Alice), and the time,$ \tau$, ...
1
vote
3answers
53 views

In diffraction process, how to describe the edge in the sense of particle-wave duality?

In diffraction experiments photons show behind an edge intensity distributions in the form of fringes. It seems to be without doubt that the edge is a part of the game. My question is, how to describe ...
8
votes
1answer
435 views

Källén–Lehmann spectral representation for massless particle?

Is it possible to write down a KL-like formula for massless particles (in particular, the photon)? The usual proof of the theorem assumes (see http://www.thphys.uni-heidelberg.de/~weigand/QFT1-13-14/...
0
votes
1answer
36 views

Are there any other tests demonstrating wave properties besides interference and diffraction?

Are there any other tests demonstrating wave properties besides interference and diffraction? How about refraction? Does it show wave properties also?
-3
votes
1answer
115 views

How can photons/particles/objects/things be massless? [closed]

How could we say a photon be massless? A thing which has no mass is seem to be just like it does not exist or we say it is nothing. It should be very less but we can't say "massless". Everything which ...
1
vote
1answer
57 views

Why we do not consider trajectories for photons/lightlike curves/radiation? I am having a term confusion

Lately I have asked a question about the trajectory of photons and almost everyone told me that I shouldn't talk about trajectories. Also people talked about photons, lightlike curves, light, ...
-1
votes
4answers
112 views

How does light travel?

How does light travel, does this not contradict the idea that going the speed of light stops time? Because if going the speed of light stops time and light goes the speed of light shouldn't it be dark?...
0
votes
1answer
24 views

How does an object in vacuum loose its temperature? [duplicate]

Well, it radiates in the infrared, I guess. But how exactly are these photons created? The atoms have some kinetic energy, which makes up the temperature. So while the atoms or molecules jitter a bit ...
1
vote
2answers
558 views

Why does wavelength determine the energy of a photon?

The professor for my first-year university chemistry class remarked that the wavelength of a photon determines its energy. Why is it that the case? I've only completed high-school physics so far, so ...
0
votes
0answers
28 views

Does a Description with Photons as Force Carriers Apply for Non-Radiative Systems?

What is the full quantum mechanical description of the statement from classical electromagnetism "the electric field of a uniformly charged infinite flat plane is constant"? By "full" I mean that I'm ...
2
votes
3answers
96 views

Justification of $P_{\text{photon}}=E/c$ in derivation of $E=mc^2$

I recently was reading up on the derivation of $E=mc^2$. Now, I came across this derivation at this link. I noticed that several lines into the derivation they throw in the equation $$P_{\text{photon}}...
4
votes
2answers
90 views

How photons can emerge quantized if their cause is continuous?

I know that photons are quantized, they are not continuous. But they are created by an accelerated charge. So how is it possible to have a quantized outcome from a symmetric continuous event? I mean ...
7
votes
1answer
565 views

Do photons decay as they travel in free space

From maxwell's equations, it occurred to me that photons are stable. Decrease in electric field creates magnetic field and vice versa and somehow there is a harmony that allows photon to exist as long ...
1
vote
1answer
109 views

Do photons have no mass? [duplicate]

My Quantum Mechanics' teacher said today on the class that photons don't have mass. I was puzzled because I knew that photons have momentum. If a particle hasn't mass then its momentum sould be $0$ ...
0
votes
0answers
38 views

Is there a theoretical derivation of Kim's delayed choice quantum eraser?

Is there a theoretical derivation of Kim's delayed choice quantum eraser? The original paper only shows the experimental data.