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.
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The energy of a photon depends on its wavelength, so theoretically when it is blueshifted it should have more energy right?
Then what if a spaceship with a solar panel on the front is traveling towards the sun at relativistic speeds. An incoming photon undergoes a blueshift from the observer on...
I am studying Quantum Optics. A single photon state will give the mean photon number of 1, as shown the following equation:
$$<\hat{n}>=<1|\hat{n}|1>=1.$$
For a two-photon number state, the similar calculation will be
$$<\hat{n}>=<2|\hat{n}|2>=2.$$
And for a coherent state, it is...
Please see my attachment of a recent observation of light traveling through a medium.
There is no source, just my observation
The packets of light appear to be visible, distinct , moving at different speeds, and display the various colours for each wavelength.
Is this normal / possible in a...
Homework Statement
Consider interactions of a X-ray beam at a depth, x, within a material. The flux density is:
density flux = $$\frac{I}{A}$$
where I is the intensity of the beam that cross a unit area A at right angles to the beam. Let dx be a small slice at the depth x and let dI(x) be the...
I recently re-read an article by Muller (https://arxiv.org/pdf/1606.07975.pdf) about the flow of time, and the possibility of time reversal given sufficient energy dissipation (basically during black hole evaporation, he concludes). Although the paper is on arXiv and not peer reviewed, Muller...
There are two polarization filters, A and B.
Polarization filter A has angle of 0° and B has an angle of 30°.
A photon is in superposition, so it doesn't have a definite polarization axis. The likelihood it's passing through a filter is depend on the difference between angle of the...
Perhaps this a question that make no sense or has no answer but...
I understand an EM wave is not like the carrier of an AM station but rather similar to a Keyed Morse Code transmission. In other words bust of trains ow waves
If my description is correct
How long the burst last?
How many...
Homework Statement
The problem I am trying to solve is the proper time elapsed along A's worldline between a photon being emitted and sent to B (which is a distance L away from it along the x axis) and being reflected and detected by A again. The question is the second part of the question...
Homework Statement
I have been asked to calculate the momentum of a photon in that has been ejected as a gamma ray after a nucleus was excited in terms of the Energy. I am confused as to whether or not I can use two different equations
Homework Equations
E=mc^2 or E=hf λ=h/p
The Attempt at a...
In quantum physics they say that the probability P for a photon to pass through the filter depends on the angle Φ between the photon and the filter polarization axis:
P = cos^2(Φ)
And if I'm not wrong, when the photon passes through that filter (like illustrated in the image above) the...
When a photon emitted by a distant quasar arrives, almost certainly has an energy less than 1.02 MeV. If it had a higher value, it likely would have decayed into particle pairs on its way to the Earth. Is this reasoning correct?
I've found this animation of an accelerated charge creating an electromagnetic wave:
http://www.tapir.caltech.edu/~teviet/Waves/field_a.gif
My question is regarding the perturbation I've encircled in green below:
Is this what we call a photon?
The light source in the DCQE experiment of Kim et al is a laser which illuminates two slits which are immediately followed by an SPDC. The latter is therefore excited coherently in two narrow stripes referred to as "slits". The output has a small amplitude of down-converted entangled pairs. The...
[Moderator's note: This thread is spun off from a previous thread since it was getting into material too technical for the original thread. The quote at the top of this post is from the previous thread.]
Field quantization doesn't require a photon picture. A measurement device that creates a...
We're told that all electromagnetic radiation consists of photons. But you never hear them mentioned when discussing low-frequency radio waves. Why not? I get that, due to the low frequencies, the energy of each individual photon would be very small, so there must be lots and lots of them flying...
If I understand it correctly, the proper time differential for a photon in flat space is zero. That is evident if the velocity of light is equal to c, so the right hand side of the Minkowski metric is equal to zero. Therefore the left side must also be zero.
My question: Is the same true for...
Wiki states: Photon upconversion (UC) is a process in which the sequential absorption of two or more photons leads to the emission of light at shorter wavelength than the excitation wavelength. https://en.wikipedia.org/wiki/Photon_upconversion
Is it possible to have the emitted light with the...
<< Mentor Note -- thread moved from the technical forums, so no Homework Help Template is shown >>
Let's say you have a laser cavity with two mirrors at either end, one is considered 100% reflective, the other 99.9%, so that a wave beam is emitted through this lower reflectivity mirror.
I know...
Hi everyone,
I have a few questions about the composition of light:
First, what is it? Is white light the result of all color wavelengths present in an area?
Second, if so, then why is there no interference in waves of light (or is there)?
Third, if photons all travel at the same speed, then...
I am wondering what would be an experiment demonstrating that photon parity is -1. It also occurs to me that one might deduce the parity from Maxwell's equations, though that might be a bit of a stretch since they are classical of course. Also, it occurs to me that parity might be assigned a...
If we pose a hypothetical universe end-state very cold, where only very low energy photons are left. Could these photons undergo a phase transition into something like a BEC?
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Hi,
if I read the article (see link) I get confused: Is it emission or reflection? If it is emission, how is it possible that the photons are emitted to one side? (Unfortenately I do not have access to the original article.)...
Maria Goeppert-Mayer described the theoretical foundation for 2-photon excitation and it was later proven correct with the advent of lasers. Today, two-photon microscopy uses this quantum physics principle. For example, if you want to excite a fluorophore that has an excitation peak at 495...
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Other than relativity is there any theory, proof, experiment, etc. that tells us a photon has no mass?
i.e. Is the concept of zero mass solely derived from relativity
Really silly question, but if we assume that our current science is correct, is it plausible that we can move faster than light in a vacuum? Say, for example, can we make the mass of something less than a photon so it then can it move faster than light in a vacuum.
I know this sounds like a...
I am about to teach some of an introductory course for bachelor students in the field of medical physics. More specifically the topic "Photon and charged particle interactions with matter" in respect to radiation therapy (again, medical physics). I know there are a lot of topics within radiation...
Homework Statement
Homework EquationsThe Attempt at a Solution
Since energy of photon is very low compared to the rest mass energy of the nucleus, I consider non – relativistic calculation.
Conservation of linear momentum gives : momentum of nucleus = momentum of photon = p...(1)...
If a (polarized) photon is absorbed by a polarization filter, does its energy go into the filter?
I am wondering if that is the case to obey conservation laws.
And if it passes, is its original polarisation direction somehow conserved?