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Questions tagged [photons]

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 ...

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Why is a dipole moment required for the polariton model to be applicable?

As stated in the first sentence of (https://en.wikipedia.org/wiki/Polariton) a dipole moment is a requirement for the polariton model to be applicable. Unfortunately I was not able to find an ...
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Understanding Bremsstrahlung

I have this problem: The Stanford Linear Accelerator can accelerate electrons to 50 GeV What is the minimum wavelength of photon it can produce by Bremsstrahlung? Is this photon still called an ...
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Pair production from two photons with same or with different spin?

Reading this questioner and reading the answer For example a high-energy collision of two photons can create an electron and a positron. This is just the time-reverse of the annihilation of an ...
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Clock of photon demon [duplicate]

If a photon was a small small guy, and he is moving at the speed of light in the vacuum space with a clock, will his clock stay still forever? If yes, Mr. Photon is basically "frozen"? When Mr. ...
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The event horizon of a black hole supposes an absolute zero in some field?

Based on the Schwarzschild black hole theory, if the gravitational pull of the singularity were to equalize the energy that a photon has by approaching the event horizon from a special angle, would it ...
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Are photons affected by Earth's gravity? [duplicate]

Just wondering if the Earth's gravity affects the photons? We can obviously think about equivalent mass of photons by using de broglie relation and then use it to calculate force of gravitational ...
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How do photons travel and what does the frequency of a photon mean?

I am pretty much confused about all this. I have researched a lot about this and many sites say that photons are particles, but this guy CuriousOne here doesn't even regard photons as particles and ...
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How to figure out if a single photon is in a quantic superposed state or not?

I'd like to know if is it possible to figure out if a single photon is in a quantic superposed state or not (i.e. it is unpolarized or not). I precise that I know it is not possible to discriminate ...
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Changing transmittivity of polarizing filters for different wavelengths

I suppose, that a polarizing filter works as described here: The polarizing filter absorbs or reflects some of the photons in the light beam, which is why the energy/power measured after the ...
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What would happen to 2 separate photons on an uninterrupted path

So I am a middle schooler and from what i understand, photons can interact with surrounding particle via gravity. If this is true, would 2 photons on an uninterrupted and completely isolated path ...
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Probability of Photoelectric and Campton decrease as photon energy increases, WHY? [on hold]

Why Probability of Photoelectric and Campton decrease as photon energy increases??
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Did the big bang create an infinite number of photons?

We will always be able to see the cosmic microwave background (CMB) at about [the age of the universe] light years away. Always. Does that mean that infinite photons were created at that time? If ...
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Difference between unpolarized beam and half H+V polarized beam

Let's say that we have got two light beams. Beam A is not polarized at all. Beam B is composed of half H polarized photons + half V polarized photons. Is there any way to measure those two beams in ...
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Pulling of Light by a Black Hole? [duplicate]

We all know that light has no mass at all. Yet we say that the gravitational pull of a Blackhole within Schwarzschild radius doesn't let light to pass. If the light has no mass, how can it experience ...
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What does degrees of freedom in a “polarisation” of photon imply? [duplicate]

While reading a QM book, the physical assumption that "adding same states of a quantum particle does not change its physics and hence the state can be multiplied by any factor other than zero" ...
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Width of the Blackbody spectrum

The Planck spectrum, $$ B(\lambda,T) = \frac{2hc^2}{\lambda^5} \frac{1}{\exp(\frac{hc}{k_BT\lambda})-1}, $$ gives the energy density of blackbody radiation at a certain wavelength, $\lambda$, for ...
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What does that sin wave of a photon represent? [duplicate]

I had an interesting thought in one of my classes, when we were talking about photons... I thought that if the speed of light is the fastest speed, and light goes in a straight line, then how come the ...
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If we were to ¨lasso¨ a photon so that it spun around a point, would it take on different characteristics or look look like other particles?

If we were to take a photon and have it go around a single point would it still look like a photon or would it look like a different particle/have different characteristics?
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Can a particle radiate in vacuum without external forces applied?

I was reading about possible and forbidden processes involving photons. First of all, the annihilation process of a pair electron and positron cannot result into a single photon because it would be ...
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What is the fundamental explanation for the existence of Electrostatic force?

To explain my question in a better way I will first talk about gravitation! Gravity is not a force and the effects of gravity are ascribed to spacetime curvature My comments: Gravity was explained ...
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What exactly happens to other electrons during an x-ray process?

What happens to the electrons that were knocked out where do they go? What happens to the electrons in the higher orbitals that are knocked out of orbit, I am sure they release photons as well as they ...
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Color and the absorption of light in quantum mechanics

In an answer to a another question, the poster states without sources the following: From a quantum mechanical perspective, all light scattering is a form of absorption and re-emission of light ...
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Do photons experience time? [duplicate]

I was just thinking about how electric field and magnetic field vectors oscillate in a Photon. but then I remember that a photon doesn't experience any time so how can these vectors oscillate if the ...
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What is the fastest possible acceleration?

Context & Question In physics, the fastest possible speed is accepted as the speed of light. No other mass has been recorded to travel as fast as the photon. What is the acceleration of the ...
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Are probabilities of a measurement in quantum mechanics absolute?

Consider an experiment in which an electromagnetic wave whose polarization is along an angle $a$ with the $x$ axis is sent through a polarizer whose polarizing direction is along $y$ axis. The ...
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How to derive derive De-Broglie's wavelength equation?

I was only yesterday learning about the De-Broglie equation $$\lambda = h/p, $$ I thought I understood it until I came across a question similar to this Now I always knew that photons don't have any ...
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What bounds does Femto photography of light pulses put on photon length?

What are the dimensions, width and length, of a photon? And similar posts repeat the assertion that photons do not have a defined length. Yet Femto photography appears to contradict this assertion by ...
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What is “Radiation damping stronger than inertia.”

I'm reading a paper on creating gamma rays in a lab and I've come across a phrase I simply don't understand; "Radiation Damping Stronger Than Inertia". As I understand it radiation damping is just ...
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Does light lose energy when it reflects from a surface?

When light reflects from a surface, at least the direction of its momentum changes. Since the total momentum must be conserved, there has to be something going on within the atoms of the surface. So ...
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Why photons do not have mass? [duplicate]

According to Einstein $E= mc^2$ so $m = E/ c^2$. So energy present in an atom contributes to its mass. So if a photon is a carrier of energy shouldn't it have mass since energy contributes to mass of ...
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Why does classical light (arbitrary mixtures of coherent states) always result in super-Poissonian statistics?

It is a well-known result that classical light (which I take here to mean mixtures of coherent states) cannot produce sub-Poissonian photon-counting statistics, with a single beam of coherent light ...
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Has any terrestrial experiment been carried out which proves whether light can be thrown sideways or not?

Let me stress, TERRESTRIAL EXPERIMENT, as distinct from astronomical observations of the transverse Doppler effect, stellar aberration and so on. To clarify what I mean by 'thrown sideways'. ...
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Can an electron absorb a photon even if it exceeds the energy required for the electron to jump up an energy level?

To clarify my question, consider the hydrogen atom. An electron on the ground state needs 10.2 eV to be excited to the second state (first excited state). If a photon with less than 10.2 eV strikes ...
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In $E=hf$, can $f$ assume any positive value? (Beginner) [duplicate]

The energy of photon is given by the equation $E=hf$, where $h=$ Planck's constant, and f=frequency of radiation. Is f quantized, or can it assume any value? If it can assume any value, then wouldn'...
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Electroweak to Electro/Weak Bosons?

I apologise in advance, this is something I just can't seem to get my head around. So it's my understanding that before the electroweak force split, there were four bosons - $W1$, $W2$, $W3$ and $B$ - ...
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Threshold energy for photoelectric effect

I'm trying to derive the threshold energy for the photon in photoelectric effect, but I'm not sure how to treat the electron. What can I assume about the final kinetic energy of the electron? I want ...
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Is it possible to have an optical version of a greenhouse? With optical fibers?

Optical fibers transport light within them using internal reflection, but the light only enters from one end of the fiber. Is it possible to somehow have light entering from the sides of the fiber (...
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What happens to a photon's speed when it reflects?

So, we have a photon going c, as they are wont to do. The photon travels exactly 1 light year where it is reflected 180 degrees and travels the same light year back to the start (our detectors). Is ...
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When a hydrogen atom absorbs a photon, what happens to the photon [closed]

When a hydrogen atom absorbs a photon, what happens to the photon? I know what happens afterward, but what exactly happens to the photon?
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How does something start interacting with the Higgs field?

When two high energy photons are smashed together they create a matter-antimatter pair. The photons do not interact with the higgs field, but when they convert into matter-antimatter pair, they start ...
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How is a photon converted into matter?

Photon is a mass less particle but still it can be converted into matter which has mass. I know the formula $E=mc^2$, but is there some kind of force or particle which converts photons into matter, ...
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Probabilistic interpretation of Malus's law

A beam of photons is polarized in the vertical direction. What is the probability that a photon will pass two filters, the first at $45^{\circ}$ and the other at $75^{\circ}$? The answer is given by $...
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Percentage increase in wavelength leads to percentage decrease in energy. (Compton effect)

In this question: What percentage increase in wavelength leads to a 75% loss of photon energy in a photon-free electron collision? My understanding of this question is that $0.25\times E_i = E_f$, ...
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uncertinity principle in photon [duplicate]

Suppose I have a em wave train.How do I know how many photon does it contain?And where are the photons?(like in the middle or more toward the end of the wave train)The frequency of light that we get ...
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What is the difference between upconversion and two photon absorption?

I have read this: https://en.wikipedia.org/wiki/Photon_upconversion And it says that upconversion is a process where subsequential absorption of two or more photons leads to emission of light with ...
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Does reflection preserve wavelength?

If a photon at a certain wavelength gets reflected on a surface, does the reflected photon have exactly the same wavelength? If not, what is the distribution of its wavelength? I know about up- and ...
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As light travels upward in the earth’s gravitational field, it loses energy, and so its frequency goes down?

I have read this question: Light frequency and time relation where it says: As light travels upward in the earth’s gravitational field, it loses energy, and so its frequency goes down. (This ...
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Is there any epoxy/sealant that is optically clear and can withstand temp up to 400C? [duplicate]

Any polyimides-type or any glue that can tolerate that temp AND be able to transmit visible light not uner 80% transmission?
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What happens when an electron in a coherent superposition interacts with a coherent laser beam?

Suppose we have an electron which may occupy three electronic states states $|1⟩, |2⟩,|3⟩$ with energies $E_{1}, E_{2}, E_{3}$. It happens to be the case that $E_{3} - E_{2} \ggg E_{2} - E_{1}$, so ...
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Does a photon box have gravitational potential, and cause GR time dilation?

I have read these questions: Does a "Photon Box" have gravitational mass? Does a box containing photons have more inertia than an empty box? And it made me curious. i understand that a ...