Photons Definition and 1000 Threads

Since we know the precise velocity of any photon, does that mean it's location is always undeterminable?

Its easy to understand how a photon can transfer momentum to a charged particle like an electron, but I'm not sure how it would interact with something like a neutron or neutrino. Could someone explain briefly?

Homework Statement A 35mW laser produces 526nm green light. What is the number of photons it emits each second? 1.9×1017 1.9×1018 1.0×1017 9.3×1016 Homework Equations The Attempt at a Solution I've been playing with E=hf and lambda = h/p ----- no success! The...

here are the problems that I need help with: http://imgur.com/a/fERMC/1 I am afraid that I know not much information about the questions. Sadly, I am enrolled in a poorly written Physics class online. I am not looking for the answers, but just how to go about finding them. The book never...

Hi I am curious about a few things i have read about light and would appreciate some help. First of all to my knowledge the speed of light is 186,000 mps and of course its impossible to exceed or reach the barrier of light for any other object other than light. But I am curious as to why...

Hi I am curious about a few things i have read about light and would appreciate some help. First of all to my knowledge the speed of light is 186,000 mps and of course its impossible to exceed or reach the barrier of light for any other object other than light. But I am curious as to why...

I suppose that momentum of virtual photons is known precisely and energy of them is uncertain. But how uncertain? Maybe let us look the simplest example: scattering on heavy nuclei. Or, there are some more simple examples as scalar photons.

hi, when an electron stays in the same electronic orbitals with principal quantum number n, with a constant energy and momentum, are there still virtuals photons that are permanently exchanged between this electron and the nucleus? I believe that the electromagnetic field is equivalent...

Homework Statement On a dark night, most people can see a 100W light bulb from at least 1 km away. Given that a 100W light bulb emits about 5W of visible light, and assuming that the wavelength is 500 nm, calculate the number of photons per second entering each eye (pupil diameter 0.7 cm) of...

Virtual photons are not "observed" because they have a deficit of energy. When they are emitted from particles momentum is conserved but energy is not conserved. The deficit of energy is accommodated with the uncertainty relation: delta_E * delta_t of the order of h_bar Now if delta_t...

I came across an article in HuffPost entitled : Does the Past Exist Yet? Evidence Suggests Your Past Isn't Set in Stone Could anyone comment on the following quote: Could you post links to this research, and comments on this experiment?

I have been looking at the new map of the universe created from data gathered by the European Space Agency’s Planck Telescope. The map has a red background containing gold flecks. The gold flecks representing radiation from fireball following the Big Bang, light that is thought to have been...

Thought experiment: An X number of lasers shoot a photon simultaneously at a single point in space. Given constructive interference is there an energy limit that can be reached? At a single point is there a limit to the number of photons that can exist?

I was recenlty watching a lecture by Feynman where is talks about particles, and how all particles have anti particles. A photon is a particle but I can't find any discussion about a anti photon. Reason?

Do photons remain stationary in the fourth dimension? Do photons age? Thanks! :)

Virtual particles confuse me a bit, because although the ones which exist for such short times in Feynman diagrams seem straightforward, the electric and magnetic forces, whose ranges are infinite, are transported via virtual particles, whereas a real photon is just electromagnetic radiation...

It is said that if you add photons into a box and close it, the weight of the box will be increased. My question is: How? Photons are understood to be massless, which is what allows them to travel at c. But, when photons are absorbed by a material body, they do add mass to that body. Now...

When the electron double slit interference pattern is destroyed during measurement detection, to determine which slit the electron passed through, the explanation is that the observation is responsible. Given that detection is done with photons that can interact and alter the path of the...

When did the first stars form? When did the first photons form?

If photons don't have mass, why do their paths "bend" in a gravitational field? This is question #8 in the FAQ and the answer provided is this: I'm trying to understand the last sentence. I must be having a mental block: why would thinking of "relativistic mass" cause identical...

Hello, If a beam of light is used in the double slit experiment instead of individual photons does each photon interfere only with itself in superposition or do the different photons interfere with each other? If detectors are used will the interference pattern still disappear? Thanks

This is just a random inquiry that's confusing me. I remember hearing at one point that the reason no object could travel at the speed of light is that an object with mass going at the speed of light would require an infinite amount of energy to get moving that fast. And that photons could do it...

lets say i have a hydrogen atom and i shoot a photon at it but the photon does not have enough energy to kick the electron to the next energy level , does the electron absorb the photon and if it does what happens ?

Why does gravitational lensing occur if photons are massless?

I was wondering what the nature of a photon is, when I was thinking about different EM wavelengths.. If you compared the distance traveled by two photons of different energies, wouldn't the more energetic one travel a longer distance (assuming they have the same amplitude)? It seems like it...

Alright, hi. I've posted one or two things on here, and have been thoroughly informed how incredibly stupid and unprepared I am to even type in the same domain as people with IQs that mine would factor into. Okay, so I read Hyperspace and am reading the Elegant Universe. I'm a dumb high school...

Why photons can't afford more than light speed? They are not limited by E=mc^2.

Can someone tell me what mass is other than particles with mass react to a gravitational field? Electrons and photons are quite similar, both are thought at the moment to be elementary particles, both exhibit wave/particle duality. Yet the electron has mass whereas the photon has none. It can't...

This may be a dumb ? , but what would happen if two black holes were coming together and when they were coming together we got a photon extremely close to their event horizons , and when the came together the photon was right on the overlap of their event horizons which way would the photon...

Last night an EE I was talking to here in San Diego got noticeably upset with me when I asserted that all visible light consists of photons, including light from such sources as the sun, an electric spark, and a lit match. I found myself being treated like a crackpot for asserting what I took to...

Homework Statement Hi I am not too sure but I had my physics exam the other day.I think it went great although I am much confused on few problems now when I come to think of them.Question first asked for me to find kinetic energy of a photon. So using 1/2mv^2 I got that value later on it...

How can a photon, or any other particle, interfere with itself? What does the uncertainty principle have to do with it? Why can't a device be used to track particles/waves? Please help with real answers! Thanks!

if electromagnetism is mediated by photons, what do photons have to do with magnetic fields? more specifically, what is a magnetic field "made" of? surely there aren't photons released by an ordinary household magnet? i have a vague understanding that magnetic attraction has something to do...

I don’t want to dismiss the obvious practical utility of photons as a model. But setting aside the wave nature of light (since it is complementary anyway), why do we need the intermediary, “photons” to explain the particle aspects of light? SR says photons don’t age because they travel at c...

Entangled “Frankenstein” Photons Entangled "Frankenstein" Photons David R. Schneider (David@DrChinese.com) Abstract: The H> and V> outputs of a Polarizing Beam Splitter can be combined to restore the original input superposition state, as long as no knowledge is obtained regarding the path...

In QED, Feynman talks about P(A to B), the probability that a photon starting at a particular point in space will travel to a different point in space (I've since learned that P(A to B) is actually the Feynman propagator, unless I was midled). What I'm wondering is - what happens if there are...

I understand that the probability of a photon refracting or reflecting between mediums is dependant on the photon's angle of incidence and the two medium's refractive indexes. How can I calculate the probability of a photon reflecting instead of refracting for example, a sheet of glass at a...

Homework Statement how many photons does the sun generate to knock one electron across the bandgap in a PV panel? I am doing a college level night school course on Photovoltaics and I have to do a short presentation on photons and how they produce useable energy. I thought it would be...

Hello, I'm quite confused about something. Maybe you all can help :) I'm not sure I understand why the science community seems to assume photons have no mass. I can understand how it wouldn't make sense to say a photon has mass by the mathematics that is used to describe the energy of a...

With two electrons emitted from a decaying atom in opposite directions, the speed can easily be greater than the speed of light between the two electrons (e.g. 0.7c in each direction). If two receivers then pick up the electrons, hasn't the information traveled between the two receivers at a...

As I understand it photons govern the electromagnetic field. I don't have an intuitive knowledge of what that means. Does anyone have an explanation, link or reference for an intuitive interpretation? So if I rub a latex balloon against my clothes and then put it near my arm, I'll see all...

Homework Statement An owl has good night vision because its eyes can detect a light intensity as small as 4.5 10-13 W/m2. What is the minimum number of photons per second that an owl eye can detect if its pupil has a diameter of 7.5 mm and the light has a wavelength of 503 nm...

Is it possible for photons to interact with each other directly?

if time has no meaning for a photon, do you think its correct to say that from its point of view that age of the universe is 0 seconds?

A quick question regarding compton scattering: if we consider the situation in which a photon incident on a free electron is scattered through an angle of 180 degrees, its energy essentially does not change. Since energy must be conserved, I assume this means there is no effect whatsoever on the...

If I fire photons at a glass, some will be reflected back and some will go through. Which ones is by deifnition random, sincee all photons are exactly alike. Is this correct?

If photon's cannot couple with other photons , then when we shoot photons through a double slit and we get an interference pattern , How are the photons interfering with the other photons , and if there is no such thing as half photon like the photon is either absorbed or it is not ...

If a photon is detected at point B having been emitted at point A, can one deduce with near certainty that it must have traveled continuously in a straight line from A to B at velocity c?

I've got three questions basically. Do photons actually have only an integer spin +/- 1, or do people really only mean the sign of its chirality? The reason I ask is that I am interested in whether the photon spin is related to its frequency. This leads to the next question. Is the basis for...

1. In a collection of hydrogen gas, 100 electrons are located in the n=3 orbit. A. What is the frequency of a photon that could have been absorbed to cause an electron to transition from its ground state to the n=3 orbit? Now, as these electrons return to their ground states, assume...