Photons are electromagnetic waves. They exhibit particle-like qualities in many situations and have zero rest mass.
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Why doesn't light kill me?
I was attending my philosophy class and in the middle of student presentations, I found myself mentally wondering off and thinking about light. After a few minutes of trying to piece together how the ...
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Neutrinos vs. Photons: Who wins the race across the galaxy?
Inspired by the wording of this answer, a thought occurred to me. If a photon and a neutrino were to race along a significant stretch of our actual galaxy, which would win the race?
Now, neutrinos ...
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If photons have no mass, how can they have momentum?
As an explanation of why a large gravitational field (such as a black hole) can bend light, I have heard that light has momentum. This is given as a solution to the problem of only massive objects ...
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Do photons gain mass when they travel through glass?
Please correct me if I'm wrong, but I believe that photons slow down when travelling through glass. Does this mean they gain mass? Otherwise, what happens to extra kinetic energy?
I understand now ...
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How can a photon have no mass and still travel at the speed of light?
I've read a number of the helpful Q&As on photons that mention the mass/mass-less issue. Do I understand correctly that the idea of mass-less (a rest mass of 0) may be just a convention to make ...
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Does a photon interfere only with itself?
I sometimes hear statements like that:
Quantum-mechanically, interference pattern occurs due to quantum interference of wavefunction of a photon. Wavefunction of a single photon only interferes ...
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How are forces “mediated”?
I hope this is the right word to use.
To me, these forces seem kind of fanciful (except for General Relativity and Gravity, which have a geometric interpretation).
For example, how do two charged ...
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What is the mechanism behind the slowdown of light/photons in a transparent medium?
So light travels slower in glass (for example) than in a vacuum. What causes light to slow down? Or: How does it slow down? If light passes through the medium, is it not essentially traveling in the ...
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How are photons “consumed”?
I have very little background in physics, so I apologize if this question is painfully naive.
Consider the following thought experiment: an observer is in a closed room whose walls, floor, and ...
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When lasers are used to cool atoms or ions, etc where does the heat go?
According to the first law of thermodynamics, sourced from wikipedia
"In any process in an isolated system, the total energy remains the same."
So when lasers are used for cooling in traps, similar ...
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How do photons travel at a speed that should be impossible to attain?
If it requires infinite amount of energy to travel at the speed of light then how photon attains this speed? Its source is never infinitely sourced.
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How does a photon experience space and time?
To an an external observer it appears that time has stopped for photon. But this relation is reflexive, so for an observer travelling with the photon it appears the universe has stopped everywhere.
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Why is the $S_{z} =0$ state forbidden for photons?
If photons are spin-1 bosons, then doesn't quantum mechanics imply that the allowed values for the z-component of spin (in units of $\hbar$) are -1, 0, and 1?
Why then in practice do we only use the ...
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What exactly is a quantum of light?
I am currently trying to learn some basic quantum mechanics and I am a bit confused. Wikipedia defines a photon as a quantum of light, which it further explains as some kind of a wave-packet.
What ...
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Does a photon have a rest frame?
Quite a few of the questions given on this site mention a photon having a rest frame such as it having a zero mass in its rest frame. I find this contradictory since photons must travel at the seed of ...
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If light is linearly polarized, does it have some spatial extent?
If light (a photon) is linearly polarized, say vertically, does it have some vertical spatial extent (perhaps in amplitude)?
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Do photons lose energy while travelling through space? Or why are planets closer to the sun warmer?
My train of thought was the following:
The Earth orbiting the Sun is at times 5 million kilometers closer to it than others, but this is almost irrelevant to the seasons.
Instead, the temperature ...
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Why don’t photons interact with the Higgs field?
Why don’t photons interact with the Higgs field and hence remain massless?
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Does $E = mc^2$ apply to photons?
Photons are massless, but if $m = 0$ and $E = mc^2$ then $E = 0c^2 = 0$. This would say that photons have no energy, which is not true.
However, given the formula $E = ℎf$, a photon does have energy ...
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What longest time ever was achieved at holding light in a closed volume?
For what longest possible time it was possible to hold light in a closed volume with mirrored walls?
I would be most interested for results with empty volume but results with solid-state volume may ...
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1answer
449 views
Why are noble gases used for lights?
I know that neon is used in advert signs due to its inertness. However, I am not entirely sure how the inertness is exploited. I think it is because Ne being inert means that after electricity frees ...
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1answer
153 views
How the inverse square law in electrodynamics is related to photon mass?
I have read somewhere that one of the tests of the inverse square law is to assume nonzero mass for photon and then, by finding a maximum limit for it , determine a maximum possible error in ...
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Why is Light invisible?
Why can't we see light? The thing which makes everything visible is itself invisible. Why is it so?
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Can you split a photon?
I was wondering if a photon is divisible.
If you look at a photon as a particle, then you may be able to split it (in theory).
Is it possible and how do you split it?
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Why do we use Planck's constant?
I have been trying to reason why energy packets (i.e. photons) are assumed to be quantized. I know this originated from Max Planck, but may someone explain why energy couldn't be emitted continuously ...
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1answer
562 views
What are the specific requirements for a do-it-yourself quantum double-slit experiment?
I was shocked to recently learn that the double-slit experiment is not only possible to do with completely ordinary equipment (with photons of course), but it actually looks rather easy. This is from ...
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Confusion regarding photons?
I'm still in high school, and while I can't complain about the quality of my teachers (all of them have done at least a bachelor, some a masters) I usually am cautious to believe what they say ...
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Tachyon and Photons
Is there a particle called "tachyons" that can travel faster than light? If so, would Einstein's relativity be wrong? According to Einstein no particle can travel faster than light.
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Why is there a photon every millimeter on earth coming from a star millions of light years away?
I've been having this confusing thought for so long now it would be amazing if someone could answer me.
Imagine this asterisk * . As you see, from the center point, lines go outwards, just like a ...
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Does the uncertainty principle apply to photons?
Wikipedia claims the following:
More generally, the normal concept of a Schrödinger probability wave function cannot be applied to photons. Being massless, they cannot be localized without being ...
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How to count photons
How are photons counted?
What is the experimental setup used to count photons from a laser or even a lamp? Of course, in the case of the lamp, I would be able to count only the photons that pass ...
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Spontaneous pair production?
So I've been looking into particle-antiparticle pair production from a gamma ray and don't understand one thing.
Let's say I have a 1,1 MeV photon and it hits a nucleus - electron-positron pair with ...
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What do ants see?
After watching some ants in my garden today, and then looking at this very illuminating demonstration, I got to wondering, about what they would see. Not specifically ants (I understand their ...
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Deriving Planck's radiation law from microscopic considerations?
In the usual derivation of Planck's radiation law, the energies or frequencies $\omega$ of the oscillators depend on the measurements $L$ of the black body. The model is such that the only ...
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Compton Scattering
Compton Scattering essentially states that when a photon of a given wavelength hits an electron the energy level of the electron changes and the photon has its wavelength changed. This seems to be ...
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Properties of the photon: Electric and Magnetic field components
Consider an electromagnetic wave of frequency $\nu$ interacting with a stationary charge placed at point $x$. My question concerns the consistency of two equally valid quantum-mechanical descriptions ...
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Have red shifted photons lost energy and where did it go?
I think the title says it. Did expansion of the universe steal the energy somehow?
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Kinetic Energy vs. Potential energy with regards to creating particles
So I know that when you collide particles with high enough kinetic energy, (kinetic energy = at least the rest mass of the particles you are making), you get particles.
How come potential energy ...
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How many percent of the visible light reaching the Earth are from other stars than the Sun?
How many percent of the whole visible light reaching the Earth are from other stars than the Sun?
Is it maybe 0,5 - 1% or is my guess already too much?
I am interested mainly in visible light, but ...
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Why do Photons want to be together?
So I've heard that when a photon flies by a atom excited enough to release a photon there's a good chance it will. Because Photons want to be together and have the same direction etc?
Is this true? ...
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Photon absorption
[sorry, this way below the level of this forum -- flames are most welcome]
When a photon is absorbed by a piece of matter that does not reflect it -- where does the photon "go"? Eg, one shines light ...
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2answers
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If photons move linearly, what's actually stopping them from passing through a microwave oven mesh?
So, my understanding is that the wavelength of a photon is the distance traveled in the time it takes it's magnetic field to oscillate. And it's inversely proportional to it's energy and it's ...
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385 views
Can the spin of a photon change during its “life”?
Or is the spin set in one of two possible states at its moment of creation and does not change for the rest of the duration of its "life"?
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Why photons transfer to electrons perpendicular momentum?
Linear antenna directed along z, photons (EM waves) propagate along x. Momentum of photons have only x component. Why electrons in antenna have z component of momentum?
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statistics for photon counts in photomultiplier
It seems that a common statistical model for the count numbers of a photomultiplier is a Poisson distribution whose parameter $\lambda$ equals to the square-root of the number of counts.(e.g. ...
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photons in expanding space: how is energy conserved?
If a photon (wave package) redshifts (streches) traveling in our expanding universe, is it's energy reduced? If so, where does it go?
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Photon statistics of an incandescent light source
We usually calibrate the cameras on our microscopes by capturing 20 images of a blurry (not sharp) fluorescent particle. For each pixel in this stack of 20 images we calculate the intensity variance. ...
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Do mirrors increase the amount of light in a room?
So if you have a light bulb in a room, and you had a tool to measure the amount of light that's in the room, then let's assume the amount of light only caused by the bulb is "1"
If you place a mirror ...
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3answers
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Why can't a single photon produce an electron-positron pair?
In reading through old course material, I found the assignment (my translation):
Show that a single photon cannot produce an electron-positron pair, but needs additional matter or light quanta.
...
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Are there “gaps” in light, or will it hit everywhere?
Not sure how to word my question.
Picture a light source in vacuum, so nothing disturbs the light (or similar conditions), 2d.
If I move very, very far away, will it happen that some of the light ...
