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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Is it possible to give photons an electric charge?

I know that photons have no electric charge and that they are stable, but is it possible to give them a positive or negative charge? If so how?
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156 views

How do photons carry information?

In cosmology it's frequently said that photons from the early universe carry information from that time. However, wouldn't they also carry data from later interactions? How do we differentiate ...
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1answer
27 views

How does the flow of photons (qty/s) vary across the spectrum? (In everyday life)

Humans see only a narrow band of light wavelengths. Many animals see much deeper into infrared. Maybe one clue to explain why we don't see IR naturally, has to do with the light intensity as a ...
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1answer
69 views

Is my calcualtion from the mass of a photon right? [closed]

The Mass off a Photon The right format can be found here: Photon E = hv E = mc2 E = av (amplitude, frequency) m = hv/c2 Mass = movement of electromagnetic fields Planck’s constant = electromagnetic ...
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3answers
135 views

How are photons made?

I mean in manufacturing a bicycle we know how to "ensemble" a bicycle, what actions and "assembly of parts". So what steps are needed for make a photon? Also is there a limit on how many photons for ...
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0answers
47 views

How can spacetime affect massless entities? [duplicate]

Why is light affected and "bent" by spacetime if it has no mass or density?
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2answers
168 views

Why does light travel as waves? [duplicate]

Why does light travel as waves instead of say just a straight line? What are the forces that make a light photon travel in a wavelike pattern?
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0answers
114 views

Is this “classical model of the photon” real?

I do not know how to phrase the question better but this article claims to have a classical model of the photon. Has this (rather extraordinary) claim been verified? Here is an extract from the link ...
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2answers
277 views

Are electron fields and photon fields part of the same field in QED?

I know in classical field theory we have the electromagnetic field. And Maxwell's equations show how electromagnetic radiation can propagate through empty space. I also have been reading about QED ...
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1answer
96 views

Question about electron-hole pair generation in depletion layer for a p-n junction photodiode

At the heart of operation of p-n (or p-i-n) junction photodiodes is the absorption of photons leading to generation of electron-hole pairs. If the diode is, e.g., reverse biased, then the motion of ...
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1answer
36 views

Why would a photon striking an electron “make both recoil”? [duplicate]

Why would a photon striking an electron "make both recoil" as I read in an answer to another question. If the photon is massless, how can it make an electron change momentum?
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0answers
22 views

Holding a photolithography mask (EUV litography) with magnets, to minimize deformation on the photomask?

Some background: what is this question about? On 20/11/2014, I visited the ASML Holding in the Netherlands, which is according to them, and according to Wikipedia: the largest supplier in the ...
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3answers
169 views

What is a photon? [duplicate]

I'm trying to get a definitive and clear answer to the question of what a photon actually is. Textbooks seem to give quite vague explanations, all starting with Einstein's idea that a quanta is a form ...
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0answers
45 views

Photons and gravity [duplicate]

A very powerful laser pointing to the empty space next to small object in space. The photons in the laser beam does not hit the object. Will the small object be gravitationally affected by that laser ...
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1answer
69 views

How can absorption spectra form if atoms can't remain in an excited state?

I have been tasked to write a research paper on stars. However, I know very little about physics in general. I am learning about how we can glean information about stars by analyzing the light that ...
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1answer
247 views

Why does light not slow down?

Clearly light bounces off of things, going really really fast. I'm curious to understand how light interacts with matter in order to bounce without: Applying force to the object Losing speed So my ...
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1answer
1k views

Is a photon technically a set of two particles?

When looking at the classification of massless particles, one finds that there is the (half-integer) quantum number "helicity" $h$. For every possible $h$ there is a certain particle kind. In the case ...
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2answers
61 views

Number of different wavelengths in the visible spectrum reaching Earth

I recognize the visible wavelengths of light extend from approximately 400 - 700 nm. But how many different wavelengths exist in that range? 300 ? 30,000 ? (400.01 - 699.99) If it's completely ...
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1answer
201 views

Relation between number of photons and energy?

Please can anyone explain it. If number of photons are increased will it increase the providing energy. Suppose, we are sending a limited number of photons each carrying energy. We have a energy ...
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1answer
61 views

Does light have a gravitational pull? [duplicate]

I understand that everything with mass does have a gravitational pull no matter how small the object, which means even a grain of sand has a gravitational pull. But light is something that exists, ...
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1answer
149 views

What is the speed of a Photon? [duplicate]

How fast does a Photon travel through space? And is gravity able to influence a Photon's path?
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1answer
41 views

where does the kinetic energy of electron revolving in nucleus go when photoelectric effect takes place?

we all have been studying that when photon is incident on alkali metal surface, photo currents are created due to ejection of electron after exceeding the work function.but the electron do have ...
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3answers
128 views

How can a photon have a frequency but not a phase?

When a single photon is emitted as a result of relaxation of an electronic energy level, it (the field) is clearly in a Fock state because it has a well-defined number of quanta. By the uncertainty ...
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0answers
30 views

Calculation of energy deposit of photon beam

Let's say I shoot a 1 MeV photon beam onto a volume. I want to know the ratio of deposited dose per path length for different materials (water and air) at a certain position (e.g. x=0) in the volume. ...
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2answers
31 views

Laser beam sensed by scattering

Can a laser beam, whether it is a IR laser or of the visible to human eye spectrum, be seen/sensed by an electronic eye like a photosensor/photodetector, not human eye, if the beam is just in air? For ...
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0answers
21 views

Gamma photon excitation of electron

Can a single high energy photon excite more than one electron in an atom?
5
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1answer
155 views

How hot is your photon?

This question comes from my answer to the question Can a cubic meter of space at absolute zero have any object with mass inside? and the related discussion under it. To summarize, I stated that the ...
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1answer
70 views

Can someone reconcile the Boltzmann transport equation with the Maxwell equations for photons/light?

Having taking courses in both physics and nuclear engineering, I've noticed that the two fields tend to describe photons/light in two different settings. In nuclear engineering, the radiative ...
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3answers
136 views

Do Photons Move in a Wave Like Pattern [duplicate]

In many pieces of literature, light is said to travel like a "wave". Does this mean the light literally propagates through space like a wave as in up and down and so on or does light move linearly ...
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0answers
28 views

The path that light travels [duplicate]

This is a question that has puzzled me for some time. As a star emits light, the light travels away from the star. If you were to pick any spot on the star and draw a line extending outwards and then ...
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3answers
85 views

Laser beam photon counting

I'd like to know if devices exist that are able to detect the single photon missing out of a normal laser beam. I am aware of the fact that single photon counters do exist, but I'd like to ask some ...
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2answers
52 views

How can solar sails be maneuvered?

Photons from the Sun are always radial to it and hence solar sails can only travel radially. Any techniques related to maneuvering?
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1answer
66 views

Under what conditions would photons interact to create pair production? [closed]

I understand that two photons colliding can result in pair production but under what conditions would this happen? Would the photons have to be in a superconductive state or is it just by chance, as ...
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2answers
547 views

Is there anything that could attract and trap a photon?

Is there any particle or anything that could attract and trap light or photon particle? Can anti photon particle attract photons and trap them ?
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2answers
29 views

What would influence two or many photons to collide and create an electron-positron fermion pair?

If there were billions of photons around in nothing - no gravity, no electromagnetic fields, etc., what (if anything) would cause the photons to interact in a way that would cause a collision ...
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2answers
165 views

Explain the notion of light/electromagnetic waves/photons to a non-physicist

A non-physicist asked me about special relativity. My explanations naturally were based on gedankenexperiments involving light. This forced the question: "What is light? It is particles, isn't? Or is ...
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2answers
98 views

Are the photons released by trees the same generated by the sun?

According to Feynman in this youtube video the photons that are released when a tree burns are sort of those that were trapped during photosynthesis. Are these the exact same photons produced by the ...
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1answer
87 views

What happens when two photons collide? [duplicate]

From a little research done it seems as though they would create subatomic particles (maybe electrons?)If so, would photon collisions technically create matter? Is this a widely thought of theory?
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1answer
77 views

What is the total matter equivalent of the Sun's output per year?

Say we can collect all the energy from the sun's output and all the particles from the solar wind. If we had an energy to mass converter and turned everything into say, carbon, how many kilograms of ...
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1answer
85 views

Can photons “stop time”?

If traveling past the speed of light causes time to reverse than does traveling in time make time "stop"? If not then how do photons/mass-less particles experience time, if at all.
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2answers
122 views

What would be the photon's effective mass in Newton's Law of Gravitation?

If we equalize the force from the Newton's Law of Gravitation to Force on a photon in a gravitional field (I don't know if there is an equation for it). What would be the photon's effective mass? (I ...
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0answers
40 views

If 2 photons collided head on, what would happen? [duplicate]

If 2 photons, in perfect synch (frequency, amplitude, etc. were all equal) and they collided head on, what would happen? Would they pass right through each other? Would they interfere, then go back to ...
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0answers
80 views

How does electron excitation work for the Bohr model with non hydrogen atoms?

I've seen a lot of explanations of electron excitation by photons in the Bohr model but they all use a hydrogen atom which only has one electron. How does the excitation work for atoms with more ...
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2answers
77 views

Is colour a purely quantum effect?

If the colour of an object is determined by the wave-lengths of light that is absorbs and reflects (?) then can colour be described as a purely quantum effect (i.e. without quantum effects an objects ...
0
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1answer
55 views

Why photons are having energy when they are massless? [duplicate]

As per the Einstein equation $E=mc^2$, the energy of the particle is depends on the mass of the particle. Or else in other terms the energy is proportional to the mass. If the photons are having zero ...
3
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4answers
280 views

How can we prove that a photon is absorbed only once?

When I first heard about the photons and the double-slit experiment my immediate thought was the following: Alright, energy is not absorbed continuously but in discrete units, photons, but nature ...
3
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1answer
121 views

Calculation of the efficiency of a Carnot engine for photon gas

I am working on a problem considering the Carnot cycle for a photon gas. The cycle has two isothermic processes at $T_{H}$ and $T_{C}$ and two adiabatic processes. The entropy of the photon gas is ...
3
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1answer
554 views

Width of a photon. And its length

Everyone is always talking about photon's wavelength. But what about its dimensions? What is length and width of it? And does it even have a point to think about such things? Or those dimensions are ...
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2answers
104 views

How can a single photon or electron create a small visible dot on a photosensitive plate?

The photon or electron is just one subatomic particle, but if it hits the film and creates a dot visible to the human eye (btw, modern technology can do this), then the dot must be a collection of ...
4
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1answer
131 views

Slower than light photons in vacuum?

This report on the BBC site suggests that optical photons have been prepared that travel slower than c in vacuum. How is this possible?