Tagged Questions

"Photon" is the name given to particles of light in the quantum mechanical understanding. In interaction where the classical and quantum mechanical understandings of light agree they are fully equivalent to electromagnetic waves.

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How do you isolate a single photon?

How do scientists/researchers isolate a single photon (for single photon sources)? How do they know they have isolated it? Is it really totally "isolated"? What is the photon isolated in? Sorry if ...
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44 views

Atomic absorption question

My book says that when a photon carrying a certain amount of energy hits an electron, that gets excited and goes on an higher energetic level, absorbing the energy of the photon. When it comes back to ...
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75 views

Do photons change velocity instantaneously?

Any object traveling at c is observed as traveling at c in all reference frames. When a photon travels through a vacuum at c, all reference frames observe it traveling at c. When a photon passes ...
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No photon interaction in free space

How can the Hanbury Brown and Twiss effect (photon bunching) be explained if photons don't interact in free space? To explain it with the influence of the two photons on the two detectors ...
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Can various wavelengths participate in C/D Interference?

My question is can multiple wavelengths or at least two different wavelengths interfere with one another? I know that they usually have to be the 'same' wavelength, but you'd think they can vary a bit ...
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75 views

Shooting a single photon through a double slit

Consider the image below. It shows a double slit experiment but with a single photon at a time. My question is as follows: Why is it that the photons always take a different path when shot at the ...
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Why are neutrinos more weakly interacting than light?

When people describe neutrino interactions they describe them as rare/infrequent due to the fact that the neutrinos are electrically neutral and have little mass, if any. Well why then is the photon ...
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Massive photon and gauge invariance of S-matrix amplitude

Let's have minimally extended gauge invariant lagrangian (with free kinetic term of EM field): $$ \tag 1 L (\Psi , \partial_{\mu} \Psi) \to L (\Psi , D_{\mu}\Psi ) - \frac{1}{4}F^{\mu \nu}F_{\mu \nu}, ...
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Why photon has a wave nature? [duplicate]

Wave theory does not account for the photon model, which was developed only to explain quantum effects like photoelectric effect. Then why do we talk about a photon's reflection and rarefaction, as ...
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If a photon has no mass, how can it be attracted by the Sun?

I read that the photon doesn't have mass, but my teacher says that the photon has mass because the sun can attract it (like in the experiments to prove the theory of relativity). I think that there ...
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301 views

Energy & Mass of a Photon [duplicate]

$$\text{Please read the whole question before answering}$$ Before I ask my question, I would like to say that "Yes, I do know a photon has no mass." I was helping someone here on P.SE with the ...
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29 views

What causes light to travel? [duplicate]

What is the force that causes it to move and why does it maintain the speed for so long? If it has no mass, why is it effected by mass?
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95 views

Taking photos without photons?

I was looking up some science news and I came across this! Blind quantum camera snaps photos of Schrödinger’s cat ...
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Photoelectric Effect - How are the electrons regained?

When the photons with enough energy impinge on a photocathode, it emits electrons. Does this mean that the solid will lose all its electron at one point? If not, how are electrons restored?
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Photons “rate of fire”

I'm not sure if this makes any sense but, do photons "discharge" from a source at an infinite rate?
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Does a reflection still transfer momentum to an mirror?

I have been recently wondering, if I take a powerful enough energy source (photon) and I have an perfect mirror exactly in front of it and assume an "emitter" shot the light towards the mirror. As ...
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2answers
78 views

Optical absorption in a semiconductor for $E<E_g$ [duplicate]

Quoting from Solid State Electronic Devices (by Ben G. Streetman and Sanjay Banerjee): A photon with energy less than $E_g$ is unable to excite an electron from the valence band to the ...
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4answers
120 views

Photons to Represent a Wave

I fear that I have a fundamental misconception about the "wave particle duality" of light, but in a related question, the answerer said, in some sense, that a light wave propagates until it hits ...
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If an atom is positively ionized, can is gain electrons if you emit photons at it?

I read somewhere that electrons and light are just electromagnetic radiation and are basically the same thing, does this mean that if you emit photons at an atom it will gain electrons?
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How to tell whether photons are entangled?

Suppose you have some sort of a "black box" system - you know nothing of its inner workings. The system has two outputs, let's call them A and B, and it occasionally emits photons - one photon from ...
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Quantum Eraser thought experiment with light photons of distinct color

I tried to recreate the Quantum Eraser experiment into a thought experiment with a few changes. It left me a little perplexed as to what outcomes I should expect. Any help would be appreciated. Lets ...
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Can a single photon be polarized non-linearly?

I want to check if I correctly understand polarization. Considering a single photon travelling in vacuum, it can only be polarized linearly under the same direction at any time, right? When we talk ...
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180 views

Is time nothing but the speed of light (or the light itself)?

With regard to relativistic effects on time, all the examples and explanations revolve around light and its speed. Especially in explanatory situations that explain this using photon clock, it seems ...
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173 views

Sequence of E and B field in radio waves and in single photons

In antenna technology we distinguish between nearfield and widefield. In the nearfield the electric and the magnetic fields are shifted by 90°. If you look closer you can see that there are two ...
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Function to fit solar radiation data

I have ground-level radiation data of solar incoming radiation from a radiometer (cosine collector) measured along the day. In the following plot you can see PAR irradiance (ie visible light) in Watts ...
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Photon striking a molecule and getting reflected

I am writing a simple simulator which simulate absorption of UV light in solution. The idea is to see if I can see Beer-Lambert laws in my model. It is not intended to be a precise simulator but ...
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What are some good resources for learning photonics?

Including the generation, transmission, modulation, signal processing, amplification, and detection/sensing of light, I am interested in getting a good understanding of photonics. Does anyone have any ...
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What is the status of massless photons traveling through a medium?

Photons in vacuum have no proper time, and they are not considered as observers and not as reference frame. But what about photons travelling through matter? Their velocity is lower than light speed, ...
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Beginner question: timelessness of massless particles [duplicate]

I am not very familiar with the quirkiness of relativity, and I was wondering how to explain this situation. If a beam of light is shining at some object at some distance from the origin of the beam, ...
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How can gravity affect light?

I understand that a black hole bends the fabric of space time to a point that no object can escape. I understand that light travels in a straight line along spacetime unless distorted by gravity. If ...
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Why are objects opaque?

I have been searching the internet for answers to this question, but haven't found a convincing one. I would appreciate any response. I understand why objects are opaque/black. For example when ...
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478 views

What trajectory has the Cosmic Microwave Background radiation taken to get to earth?

I have a few related questions: Where is the CMB coming (emitted/reflected/remitted) from? When CMB hits the earth, is that the first thing those photons hit since they were emitted 400 thousand ...
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Discrepancy ( or Confusion ) in the mass of photon

$E$ = $mc^2$ And also $E$ = $hf$ (f - frequency) And hence Einstein said $m$ = $hf\over c^2$ And so photons have mass But later he also said $M$ = $M_0\over \sqrt {1-v^2/c^2}$ Where if we put $v ...
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Is there any acceleration of light? [duplicate]

I find it hard to believe that photons always travel with 3 x 10^8 m/s just from the start. But there must be some acceleration of light. Maybe huge or taking place in picoseconds. So what maybe the ...
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3answers
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Is the energy of a photon continuous/discrete?

I was struggling today with this question: does a free photon have a continuous energy spectra? Free means in no context of any energy system (eg. an atom, em field). Although I'm asking myself if ...
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How do photons know they can or can't excite electrons?

This might be a stupid question, but nonetheless, it has been bothering me. If you take a photon, make it go through some atoms in a solid, liquid or whatever, then you have the chance of this photon ...
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Understanding EM Fields

I am an electronics engineering major and some questions arise when studying communications technology that utilizes wireless technology. In particular, I am more of a complete picture kind of person, ...
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What is the relationship between the electric field E and the magnetic field (aka magnetic flux density, magnetic induction) B of a single photon? [duplicate]

I'm looking for a formula for light, for example with 660 nm wavelength, which describes the maximum of the amplitudes for the wavelength of the electric and the magnetic field of the propagating ...
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180 views

Intuitive reasoning for why short wavelength photons pack more energy?

The energy equation is straight forward, yes, but is there an intuitive reason for this?
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How many subatomic particles can absorb/emit photons?

Is the electron the only subatomic particle that can absorb and emit a photon?
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Why are results of Bell's experiments considered to “break realism”?

Related to my previous question (Why would classical correlation in Bell's experiment be a linear function of angle?), as a newbie in quantum mechanics, I am also unable to find the reason to why ...
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Polarizing beam splitters for X-rays?

What is the lower bound for the wavelength concerning polarizing beam splitters? Especially I ask for interferometer experiments with single photons. Of course I know that they exist for all ...
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Output of a beamsplitter with photon number (Fock) state inputs

Given a beamsplitter drawn below, where $\hat{a}$ and $\hat{b}$ are input modal annihilation operators, transmissivity is $\tau\in[0,1]$, and output modal annihilation operators are ...
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What makes photons travel at the speed of light? [duplicate]

Photons are the only elementary particles which can travel at speed of light. What are the qualities of the photon that enable it to travel with the speed of light?
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Electron transition creating Photons

If the transition of the electrons result in production of photons, Is photon creation is instantaneous? If Yes,At what moment rightly the photon gets created? Else, Will the photon be stationary ...
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Detect missing frequencies in a frequency distribution

I have photons with a frequency distribution where one frequency is completly cut out. For example a frequency distribution like that: My question is: How precise can the position (frequency) of ...
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How would an X-ray mirror work?

I was wondering if light can be reflected how can someone reflect X-ray of what material does it need to be made of and is its design completely different to that of our original mirrors? Does this ...
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Faraday Effect does light bend or lose energy?

I was reading upon Faraday effect when it said Faraday effect causes a rotation of the plane of polarization That in mind, does this mean the light can be bent around or does the light loose ...
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If I'm running away from chasing gamma photons, I can see them, right?

Suppose Bruce Banner goes back in time, convinced that the Hulk is a stupid menace. Let's say he also borrows Quicksilver's speed abilities (maybe the Flash is more appropriate, but based on the ...
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162 views

Redshift of Cosmic Microwave Background

Does the cosmic microwave background radiation have a red shift parameter z? If so what is the value for z?