Photons Definition and 1000 Threads

Title says it all. Also, do photons in a vacuum travel in a straight line? I find that kind of strange. Also, are gluons massless or practically massless? How are gluons detected?

photon is a particle. then how come it does not have mass?

I know about the law of conservation of energy, and I understand interference effects conceptually, but when I put the two together I'm a little confused. I know that the energy of light must simply by transformed in destructive interference...but where does it go and how? If the...

What is the ratio of energy contained in photons vs energy contained in neutrions in the present universe? Also, how is that ratio changing with time? Thanks.

Something has been bugging me ever since I learned about Bragg's peak (and how it compares to x-ray attenuation) a few years ago... I understand there are probably advantages that photon therapy has over proton therapy, but what are they? Cost? Feasibility? Probably a dumb question, but...

I have been wondering why photons can't go through matter and electromagnetic fields mostly unaffected while neutrinos can. Neither of them have an electric charge as a particle, and the basic description I see about neutrinos is always that "they are unaffected because they have zero electric...

Imagine I am sitting on a lead ion and fly happily through the LHC tube :approve:. Suddenly I feel an strong force pushing me sideways to the left. A physicist sitting in the lab frame tells me later, that I have been going through a dipole magnet yoke with field lines from top to bottom...

What would happen if all photons had (slight) electric charge? Would we just not be able to see? Or would we not exist at all? Why? If they were negatively charged, would they repel electrons and attracts to the nucleus of an atom? What consequence would this have?

Is there a known quantity of CMb phtons? Presumably we can only receive a finite amount in our detectors, but is that due to the fininite distance to our comsic horizon? But if the universe were infinite would it have emitted an infinite amount of photons from the CMb/ Would everyplace in the...

Sorry if this is a noob question or if it has been answered before or if I'm just misunderstanding the physics involved but this has been keeping me up at night and it'd be nice to have it resolved. If E=MCsquared implies that greater energy equates to greater mass in a particle, how is it...

Do photons vibrate or oscillate in any way?

I'm sorry if this is a silly question and please forgive me but, if you split photons into two by any medium or matter can it entangle photons? Do the photons have to go through a beta barium borate crystal or any other crystals? Are there any alternatives to split photons? Please provide good...

im just curious and i just want to know, do you need a Beta-barium borate crystal to entangle photons? are there any alternatives? can you use sodium chloride crystals as a possible option? what makes a Beta-barium borate so special and different from any other crystals? please provide good info...

I was wondering whether it was possible for an extremely high energy photon to exist, or if there's a limit to the energy in just one photon. And I'm talking REALLY high energy here. Like twice the energy of, say, the gamma rays released in a supernova. If this is possible, what is that photon...

Hello everyone! It's pouring with rain and the thunder is roaring. I was sitting outside watching the lighting and I had a strange thought come to me, the lighting is producing photons correct? What happends to photons after they are produced? Do they keep on moving through things just not...

For electrons in some atom to absorb a photon having some amount of energy, must this energy be (exactly) equal to the difference between the two energy levels?, can't it be absorbed when its energy is more than that difference? Because in the case of (exact-equality), it would be hard for an...

My name is Joe Fiero. Ever since I was a little kid, I loved science, especially science fiction. Sliders, Back to the future, Star Trek. I never had a chance to get a degree in the things I loved the most because I came from a poor family... which has lead me to a path of self education and...

If photons exist relatively unbounded by time, then does this mean they're outside of time, or experiencing past/present/future all in the same instance? Does this imply that they can match the quantum state of any pair photon/electron within some range, which is based on the charge of the...

Hi Guys, I have a doubt. When we think of a modulated wave, consider frequency modulation for example, does the wave contain photos of gradually changing energy (or frequency)?

Homework Statement This is my problem: (5th part is not needed) The problem is I took a bit too complicated course for me and I don't know how to solve this. Specially I need help with 3rd and 4th parts. I will very much appreciate the help. Thank you in advance.

In the electromagnetic picture, different frequencies of light waves produce different strengths of diffraction/refraction. In the quantum picture, a photon's energy corresponds to its frequency by the Planck constant E = hf. The solution of Schrodinger's equation for a free particle...

Hey, We can observe the build up of photons on a photographic plate, but we can't observe this build up with our bare eyes. i.e. without needing a photographic plate - just by looking like how we look right now. how come?

Hi there, How can I find out how many photons would land in each areas, for the following patterns: http://www.bbk.ac.uk/tpru/BasilHiley/QuantEraserLight.pdf - page two's image (screen B) How many photons make up 'eraser no photon' pattern, and where each is. Likewise for the 'eraser yes...

Hi, new here. This came up briefly elsewhere and we didn't have the cerebral fire power to get very far with it. Consider very, very long wavelength photons, (or conversely, very very low energy photons) produced inside the sun. Wavelengths we are looking at are in the range of 1 light...

I was wondering, well basically if photons carry information about themselves that is interpreted by our brain? I ask because I was thinking about things like color and distance. Correct me if I'm wrong but we see different colors because of the way the molecules or elements that make up an...

Hi All, I wonder if the modulation of RF waves (Amplitude Modulation, Frequency Modulation, and Phase Modulation) can be explained in terms of photons. Thanks, Srini

How does the exchange of virtual photons result in an attractive force (for example between a proton and electron)?

This has been discussed in a number of threads and in FAQs. I was wondering what constituted a rest frame as nothing in the universe is at rest, if you work the figures out we are moving at around 2.5% c. In another thread I found out that at rest simply meant not accelerating. This means...

Hi sorry my english I am french. :) So I was wondering what's the direction of light? I understand light is composed of photons and those are released when electrons change orbit. But if 10 000 photons are released what direction will they take and why ? Tell me if I am wrong about some...

There is something that I don't understand .A free electron radiates photons in every possible direction as long as it exists so it emits an infinity of photons with Infinite energy ?

I understand the classical view of EM fields as being (theoretically) continuous. What I don't quite get is how this can be reconciled with the QM view of photons coming only in fixed frequencies (The electromagnetic field may be thought of in a more 'coarse' way.). Is the number of possible...

When electrons gain enough energy to move out to a higher energy orbit then back to their ground state, why do they release a photon? Also, what exactly is 'electromagnetic' about light?

And still be re-emitted at the same wavelength, even after being absorbed? I imagine visible colors, to hit a dark colored surface and become absorbed. In that process some of the object's electrons (I believe the outer shell) become energetic or is raised higher. To achieve equilibrium, it...

Hi Guys, I have a question. Can we attempt to explain the phase change of a carrier wave in terms of photons? For example consider GPS signal. It is BPSK modulated, in which phase change of 180 degrees happens for multiple of 1540 cycles of the carrier. How is the phase information...

Are photons effected by traveling through electric or gravitational potential differences? If so, how so?

Hi, I don't quite understand which are the fundamental processes for production of photons that are emitted by a "black body". Usually this is explained by considering a cavity in thermodynamic equilibrium but I am not interested in this. I am looking for a more practical description of this...

I've understood for a while that a black hole is made more massive simply by shining light on it; the energy of the photons "goes towards" (for lack of a more informed/accurate term) the mass of the black hole. Also, a couple weeks back, someone on the forums said that if one had a container...

Which of the following is consistent with experiment/observation. When light is reflected off of a material, what happens to the photon? A. Is it absorbed by the electron or lattice and then re-emitted? OR B. Does it somehow just reflect/bounce off the electron/lattice? Kind of...

I had an irresitible urge to draw this...

Quantum Electro Dynamics, the quantum theory of the photon, describes the photons interaction with electrons and this is what I beleived created the electromagnetic field. However recently I've heard a disscusion that virtual photons and their interaction with electrons and the polarization of...

I was recently wondering about this. A very high energy photon cannot transform into any collection of particles with mass without interacting with another photon or particle, else it is trivial to show energy/momentum cannot be conserved. Interacting with another photon allows...

Homework Statement (Not homework, just a textbook question I'm confused about) Two photons travel along the x-axis of S, with a constant distance L between them. Prove that in S' (moving at velocity v w.r.t S) the distance between these photons is L\sqrt{\frac{c+v}{c-v}} Homework...

I am posting this under the belief that velocity affects mass and time, if my understanding is incorrect please correct it. If a photon is traveling at C then theoretically does it have an increased mass compared to a photon that is "at rest"? And if a photon is moving at C then does it...

Hello again, After asking for a better way to visualize electrons around a nucleus (and receiving one - thank you alxm), I am now left wondering about photons. How should I go about visualizing them? I have heard that they have a wavefunction, just like electrons do, but I would like to...

Do photons contribute to the gravity? Are there any experimental results like two parallel laser beams attracting each other?

Quick question: photons do not interact with other photons photons do interact with electrons photons do interact with protons (I think) so do they intereact with neutrons? How could you tell, if the energy state of the neutron changed from absorbing a photon?

imagine a photon (travelling with the speed of light) is moving straight towards a huge mass say 10^10 Msun. what will happen to its speed/energy as it comes closer to it?

Suppose I had some plasma in box with walls that allowed nothing thru, photons, plasma, energy. Now heat the plasma and maintain some temperature T (ignore the difficulty in heating the plasma with the above walls, just assume you can). An approximation to this might be some small region of the...

Locally, photons "blue-shift" when falling down a gravitational field. What happens when they arrive at the Planck frequency? Do they turn back into matter?

I have noticed in the past that light travels through water relatively undisturbed (I have noticed that there seems to be some small amount of light reflected, but most seems to pass directly through). How does this happen, in terms of photons encountering particles? I once thought that...