The photon (Greek: φῶς, phōs, light) is a type of elementary particle. It is the quantum of the electromagnetic field including electromagnetic radiation such as light and radio waves, and the force carrier for the electromagnetic force. Photons are massless, so they always move at the speed of light in vacuum, 299792458 m/s (or about 186,282 mi/s). The photon belongs to the class of bosons.
Like all elementary particles, photons are currently best explained by quantum mechanics and exhibit wave–particle duality, their behavior featuring properties of both waves and particles. The modern photon concept originated during the first two decades of the 20th century with the work of Albert Einstein, who built upon the research of Max Planck. While trying to explain how matter and electromagnetic radiation could be in thermal equilibrium with one another, Planck proposed that the energy stored within a material object should be regarded as composed of an integer number of discrete, equal-sized parts. To explain the photoelectric effect, Einstein introduced the idea that light itself is made of discrete units of energy. In 1926, Gilbert N. Lewis popularized the term photon for these energy units. Subsequently, many other experiments validated Einstein's approach.In the Standard Model of particle physics, photons and other elementary particles are described as a necessary consequence of physical laws having a certain symmetry at every point in spacetime. The intrinsic properties of particles, such as charge, mass, and spin, are determined by this gauge symmetry. The photon concept has led to momentous advances in experimental and theoretical physics, including lasers, Bose–Einstein condensation, quantum field theory, and the probabilistic interpretation of quantum mechanics. It has been applied to photochemistry, high-resolution microscopy, and measurements of molecular distances. Recently, photons have been studied as elements of quantum computers, and for applications in optical imaging and optical communication such as quantum cryptography.
Is theory around Delayed Choice remote polarization entanglement swapping of photons derived from Time Dependent Schrodinger equation (TDSE) or Time Independent Schrodinger equation (TISE)? I say the answer is no. I collectively group TDSE and TISE under the umbrella SE. And the following...
So there was this question:
The first option seems to be the only correct answer.
$$\lambda_e=\dfrac{h}{\sqrt{2m(KE)}}$$. The answer would be correct if ##KE \approx eV##
The option mentions that ##eV>>\phi## so ##\phi## can be ignored.
But I don't think that necessarily means that the...
I suppose that when carried out a Poisson spot with photons one at a time
should have to be observed.
I tried to find such experiment but i got 0 result. it seems that nobody cared
about that. But i think such experiment would be very important as it will show
that the wavefunction can have...
In their articles on the Heisenberg Uncertainty Principle Wikipedia says "there is a limit to the precision with which certain pairs of physical properties, such as position and momentum, can be simultaneously known. In other words, the more accurately one property is measured, the less...
I'm asking mainly about part (c). Within the context of BBN, I'm a little unsure how you account for different baryons (i.e. does ##n_b## include neutrons, protons, hydrogen and helium, given that helium itself contains both neutrons and protons?)
For completeness, for part (b) I would just use...
I realize that something I thought I understood about a beacon approaching a black hole I am unsure of.
My hypothetical -
I am at a safe distance from as simple a black hole as it makes sense to discuss. I launch a beacon at it, and I calculate that in one hour of my own proper time the...
Is it theoretically possible for the expansion of the universe to red-shift the energy of a photon all the way to zero? If so, what happens to the photon? Or does the photon's energy only approach zero as an asymptote?
I believe that when a photon is refracted it slows. Why is it that the wavelength decreases but that its frequency stays constant?
Does this imply that the photon has not lost any energy in the process of slowing down given that E=hf?
Thanks
I believe that when a photon is refracted it slows. Why is it that the wavelength decreases but that its frequency stays constant?
Does this imply that the photon has not lost any energy in the process of slowing down given that E=hf?
Thanks
I've been told that a photon doesn't lose energy as it travels through a vacuum because it doesn't experience time. However, general relativity states that any energy creates a gravitational field that travels away from the energy at the speed of light. Doesn't this imply that a photon once...
Imagine a special box made of inward facing mirrors. These mirrors have zero mass and are perfectly reflective. A single photon is inside the box bouncing from side to side between the two mirrors of the sides of the box. The photon is perfectly preserved in this state, and loses no energy...
When a photon interacts with matter and diffracts, the photon seems to interact with the area of its wave front, determined by an aperture even if it is only one photon. But how far does it interact in depth? Does it always "feel" the whole crystal? Can we assume the photon is reflected by the...
I am more so stuck on where to start with this problem. I know dividing the photons per second by the area gets me the photon per area, but I am not sure how the distance is related to this part of the problem. If anyone can help, thank you.
The fact that a photon moves only through space (this is what I have read, it can be wrong), not time is said to be the reason why it has so long lifespan, much longer than the calculated lifespan of the universe. Is this wrong? if so, please explain why.
Suppose a photon from the sun's photosphere, initially traveling toward earth, is absorbed by an atom in the sun's chromosphere. The electron then transitions to its first excited state and spectral darkening is observed at a distinct wavelength on earth. I've read that the electron only stays...
We know from double-slit experiments that singular photons behave like waves, so I expect that one photon would undergo refraction when entering, with an angle different than 90 degree, into water, glass or other transparent material. Is that true?
If the refraction occurs, than the speed of...
An electron requires an "exact" wavelength photon to transition from one level of an atom to another. Yet the wavelength of a photon has a a continuous probability distribution, implying that the point probability of achieving an exact wavelength is zero. One can only talk meaningfully about...
Bob lives on top of a skyscraper which is 1000 meters high.
There are exactly 10 meters between 2 (glass) walls in his penthouse apartment.
Between these walls, - a photon moves back and forth (is reflected) for exactly 100 billion years.
Bob can measure the elapsed time to be...
Let me start with my understanding of a photon. A source emits a single photon, which can be described as an excitation of the EM field. This excitation radiates outward, producing isochrons which in pure vacuum would be spherical. Then at some point the photon is absorbed by some atom. By...
I am sure this sounds silly but..
Between being emitted and interacting, a photon gives us no information as to where it is in space. If we know both where a photon was emitted from and where it then interacted, we can say that it travelled in a straight line. But we actually dont know.
So in...
According to the minimal statistical interpretation (Ensemble interpretation?) if a photon doesn't have "pre-programmed" properties or hidden variables, which determine whether or not it will pass through a filter, how does any photon pass through a given filter, or why would it fail to pass...
Let's assume an atom consists of the nucleus and electrons as point particles. Take the inertial frame to be that of the fixed laboratory. Its total energy consists of the total kinetic and potential energy of the system of particles.If an electron absorbs a photon of energy E, the total energy...
I am wondering why the photon is necessary at all. Is there experimental evidence of its existence? My understanding is that it experiences no time or distance. So if this is true why do we need it at all? Why not just say that a particle here interacts with a particle there. Do we use the...
This YouTube video, with the same title I have given this thread, reports on an experiment.
He sets up an interference experiment. The light source is a HeNe laser. The light passes through a beam splitter then through two paths. The shorter path being about 0.26 meters, the long one about...
Consider a source emitting a beam of photons. These photons pass through x thickness of material. The attenuation coefficient of the beam \mu is known.
We can write this formula
If I'm not wrong, this formula tells us the number of photons that passed through the material of thickness x...
(For me to understand, please be mindful to avoid a bunch of jargon)
I'm not sure if the proper word is wavefunction or superposition, and didn't find anything in a search of the difference between the two. So will elaborate on the question in my own words.
To begin, as far as I undestand...
What is the velocity of a photon through the four dimensions?
What is the velocity of a photon through the three spatial dimensions x1, x2, x3?
What is the velocity of a photon through the fourth dimension x4?
Any wave mass term decays, similarly if I want to explain redshift by considering massive photon, how much should be the mass? Is it less than today's upper limit.
Solution of wave equation ##□ϕ=0## gives a wave that doesn't disperse over time.
But wave solution of the form ##(□+m^2)ϕ=0## has...
Hey all,
I just wanted to double check my logic behind getting the Fourier Transform of the following Hamiltonian:
$$H(x) = \frac{ie\hbar}{mc}A(x)\cdot\nabla_{x}$$
where $$A(x) = \sqrt{\frac{2\pi\hbar c^2}{\omega L^3}}\left(a_{p}\epsilon_{p} e^{i(p\cdot x)} + a_{p}^{\dagger}\epsilon_{p}...
"Superfluid dark matter in tension with weak gravitational lensing data" (Mistele, McGaugh, Hossenfelder)
Regarding this paper, Sabine Hossenfelder tweets
One comment summarizes this as
I don't know whether it is an energy of a photon emitted by a deexciting molecule, or if it is an energy of laser's photons. Here is an example of such spectrum:
For example, that value of wavenumber ##3000\, \mathrm {cm^{-1}}## is an energy of an emitted photon or a photon from laser? And that...
Hi,
What is the energy dependence of the Equivalent photon approximation? For this approach to be valid, what is the maximum center of mass-energy. As know, this approach is an energy-dependent approach. Can this approach be used to calculate, for example, at a center of mass energy of 100...
Suppose the EPR* concept were true as it would be applied to entangled photon polarization. (Please note: I am not saying it is.) They thought QM was incomplete, because there must exist "elements of reality" (hidden variables) that supplied the highly correlated results on entangled particle...
Hello! I have some questions regarding the photon emission and whether the atom recoils or not.
When an electron in an atom emits a photon. One can calculate the energy of the photon by the difference between the energy levels from where it left to which it returned.
Let’s say it jumped from...
If I put this in technically correct terms, to enable a local symmetry related to electron phase change, we need to introduce a spin 1 field which is identified as electromagnetic field.
Yet there are other spin 1/2 particles. Say, what about neutrino? As it does not couple with electromagnetic...
How is it treated or what Feymann's rule applies to a virtual photon in an external leg? I would like to calculate the modulus of squared amplitude for the process
e-γ*→e-γ
where the * indicates that the photon is virtual. I've never dealt with virtual particles on a external leg and would...
I was reading a recent physics article on the google home page that stated that the current theory of mass is that it is a photon moving at light speed but stationary in space. My analogy of this was like a photon moving in a circle but it is not moving. I wish I could sight the article but...
Hello,
Happy New Year 2023 !
Interested in spontaneous parametric down-conversion (SPDC), and the possibility of creating entangled photon pairs, I studied several possible configurations with type 1 and type 2 nonlinear crystals.
When using these crystals, the dominant phenomenon is second...
A photon in QFT is defined in the same way as all particles. That is they denote a set of quantum states that transform in the simplest possible way under Poincaré transformations. Properly this is known as an irreducible representation (irrep) of the Poincaré group. You can classify these...
Photon is real object, a gamma photon can create a pair electron and positron. But if photon is a reality object then why itself is not a inertial frame so in this frame its velocity is equal 0?
I have seen many tutorials that provide steps how to transcribe a Feynman diagram into algebra, for instance [here]:
However, I have never seen the final line of the calculation converted into a real number. What are the steps to get from the algebra equations transcribed using the Feynman...
Hi there!
High school physics teacher hoping to pick the brains of people who know more than I do here.
I'm curious whether the rate of photon emission has any noticeable effect on the diffraction pattern generated by the double-slit experiment.
To be clear: I understand a diffraction pattern...
In relativity, momentum of a body is given by ##p=mv/\sqrt{1-v^2/c^2}##, but if mass is exactly zero and velocity is exactly ##c##, how is the photon momentum even defined? I don't think this problem can be resolved by simply stating the other formula relating energy to momentum, since it was...
Let's say that we're sending a collimated beam of EM radiation through a slit that's 3 cm wide, and it diffracts and forms a clear interference pattern on a screen, with the bands of brightness and darkness, or of high and low intensities.
And next, we reduce the intensity of the beam until it...
Are there any kind of observed and experimentally verified processes or mechanisms where photon emission occurs and which are directly cause by spacetime expansion in some way?
This is just a curiosity to me. My interest is from the position of a layman (as you will see from my description below).
In the double slit experiment it shows a wave passing through both slits and interfering with itself to create an interference pattern.
This is how I understand it...
From...
When a photon is absorbed, electrons move from a lower energy level to a higher energy level, so my answer is a, b, c, and f.
I don't understand why the solution is b, c, d, e. Can electrons in this case move from a higher to lower energy level?
Thank you.
I can't find the anwer on this anywhere, so I hope I may ask it here.
My question: In a standard double slit experiment, according to the Many Worlds Interpretation, does the photon create different worlds with different impact locations of the photon?
So, without measuring which way...