Photons Definition and 1000 Threads

I'm a "layman" when it comes to physics and I read in the FAQ that a photon is not a real particle but is described as one for the benefit of lay-people. I read that 65 billion neutrinos pass through a square centimeter every second so I wondered how many photons pass through a square...

Homework Statement Two photons in the laboratory system have frequencies \nu_1 and \nu_2. The angle between the propagation directions is \theta. a) Write down the expressions for the total energy and momentum of the photons in the laboratory system. b) Find the photons’ frequency...

p=mv then for a photon p=0*c means p=0. And also ke=1/2pv which is ke=0 and E=mc2 means E=0. please use easy words and we descriptive.

Derive the relation Δn.Δσ ≥ 1/2 where n is number of photons in an EM field and σ is phase Using heisenburgs uncetertainty principle? Tried subbing in frequency into heisenburgs uncertainty principle to get to the number of photons and to get rid of mometum is this the right line? Dont...

Homework Statement Suppose we set up a sequence of three polarizers with orientations 45 degrees, 75 degrees and 45 degrees, where the angles refer to how much each polarizer is rotated relative to the vertical direction. If we send three vertically (i.e. 0 degrees) polarized photons in either...

anybody?

This follows some questions/points made in my light and sight thread. I have been trying to work out the relationship/difference between photons and waves. I now think that a photon is a discrete particle like amount of energy needed to jump an electron from one orbit to another, perhaps call...

Hi guys, I have a question about the difference in the time it takes a neutrino to escape the core of the sun compared to the time it takes a photon to escape from the core of the sun. Basically, my question is: what is the difference between photons and neutrinos that makes neutrinos very...

If we have two groups of photons; each group consisting of two entangled photons. We allow one of the photons from each group to interact with another object. If we perform a polarisation measurement on each photon of one group, will the photons in the other group, independent of whether...

what are photons made off?? this might be a stupid question but lets take a proton or a neutron these "elementary" particles are made up of quarks, does photons in its particle state follow the same pattern?? if yes then what constitutes into a photon?? thanks

# of photons in a mode (in a blackbody) I've been going over a proof again concerning the thermal average number of photons in a mode of a cubical blackbody of length 'L' at equilibrium with a reservoir of temperature 'tau' (has a small hole in it, etc. etc. etc.) The logic went as usual...

At first, I want to say that electromagnetism is my weakest physics branch so this question might sound silly. Electromagnetism unified electricity with magnetism and the quanta of electromagnetic force is a photon. Is there any link between magnets and photons? Is there any link between...

This question has gone unanswered by our friends in nuclear/atomic threads. My question relates to a solitary Tc^99m decay in particular, and to gamma rays in general. If light is a collapse able wave function, are different wavelength energies the same, ie gamma, x, radio, etc. My...

What I have been taught in high school physics says that all particles can be interpreted as waves, and all waves as particles. By definition, particles have volume, and therefore must have mass (in a physical sense). Photons are always regarded as waves, but therefore could always be...

Hi Would anyone help/advise me? I've done 2 experiments as part of my radiography degree. One was to investigate the effect of the ISL on a beam of x-ray photons. I could understand this, produced 2 graphs (Mean reading against distance (uGy) and Mean reading against 1/d squared) and wrote a...

I understand how gravity can affect photons or light waves (Einstein's equivalence principle). But I was wondering if there are any theories that predict that a photon might somehow acquire mass in the presence of a singularity.

It is said in particle data sheets that photons and gluons both have 0 mass, 0 electric charge, and a spin of 1. If the two particles both have the same properties, then how is it possible to tell the difference between them? Can a complete table of properties comparing the photon with the gluon...

While reading on Cerenkov radiations I've been coming across statement to this effect: It has been noted that the number of photons at a particular frequency or wavelength, as it turns out, is proportional to 1/l2 How is that (mathematically) so?

Hello, iam new to polariton lasing and have to hold a speech about it. So I've got some questions and it would be great if someone could answer them. In a polariton laser, lower polaritons form a quasi bose einstein condensat at k=0. [My most important question:] I don't get it when the...

I read recently that the "number of photons emitted by a charged particle is inversely proportional to wavelength" with regard to Cerenkov radiations. (The wavelength refers to the radiation which is of comparatively shorter wavelength, towards the blue-end.) I was looking for a more detailed...

When you create a pair of entangled photons, are they simultaneously in a superposition of V and H, and 45 and 135 polarisations?

Please teach me this: What is collinear photon (emission)?I do not understand why call ''collinear'' photon. Thank you very much for your kind helping.

a massive body like a star creates a warped spacetime in its vicinty. this warped geometry of space is reflected by the geodesics appropriate to its mass. a photon passing by this massive object is not, as per GR, "attracted" to the star via some "force", but rather simply follows what it sees...

Suppose a Fock state contains 2 photons, both in the same spacetime mode and having the save (vertical) polarization. So we can write this state as |2>, or, if we want to emphacize its vertical polarization, we may write |2v> or |2v,0h>. Suppose now we want to measure polarization in the...

Does the photon number state of n photons in the same mode (i.e. Fock state |n>) constitute a Bose-Einstein condensate of photons?

And what determines the wavelengths of the emitted photons? In jumping from one orbital to a lower one, how many photons does an electron generally emit? Is it just one, with a wavelength determined by the distance jumped between orbitals, or many? In the case of an electron being...

Homework Statement Use the Boltzmann distribution function to calculate the temperature at which 1.00% of a population of photons will have energy greater than 1.00 eV. The energy required to excite an atom is on the order of 1 eV. The Attempt at a Solution I attached my attempt but...

I'm trying to follow the logic to the quantum theory of the entanglement of light. I'd like to ask a question about one of several problems I'm having with the entanglement. If: Photons (Light) have orthogonal electric and magnetic waves. And: In discussions of polarization of light for...

Homework Statement I have this task: A collimated monochromatic beam of photons with intensity 10^20/s and energy 10 MeV is directed to a iron absorber with thickness 3 cm. What kind of interactions are expected? Suppose, each interaction removes one particle from the beam. I need to know...

Homework Statement I am trying to answer a relatively simple question. I have been asked to compare the number of Photons in 100W light bulb and a 100W FM Radio per second. Having crunched the numbers it appears that an FM Radio wave gives out more Photons per second than a light bulb. Is...

Hi. Was wondering if anyone could recommend some good introductory quantum optics textbooks? I have a good grounding in quantum mechanics, but have never looked at quantum optics. Basically my problem is that I am doing my project work in this field(to start in a couple of months) and have...

In solids it is the interaciton b/w the phonons and photons that give a lower effective speed. not absorption & re-emmision. (see ZapperZ's post: https://www.physicsforums.com/showthread.php?t=511177 ) but in amorphous glass there are [B]no[B] phonons. So why does light 'slow down'...

Is it possible to accelerate particles like light in some type of particle accelerator? if it is possible why? if it's not why not?

how are scientists able to distinguish between photons? Photons are smallest quanta of EM (electromagnetic) radiation. How are scientists able to distinguish between photons except by correlating with position in time-space, frequency, spin etc? For example: In the article below: How are...

Photons activate hormones in us which cause us to wake up. I'm wondering if there is a different between the photons coming from the sun and the photons coming from a light bulb? Do these both have the same effect on the body? I've put this in the classical category because of optics.

Hi people, Time-dependent perturbation theory allows for transitions to excited states, through a sinusoidal perturbation whose frequency is smaller than the energy difference between the states. (That is, P_{a \rightarrow b}=\frac{sin^{2}[(\omega_{0}-\omega)t/2]}{(\omega_{0}-\omega)^2}...

Relativity states that as anything approaches the speed of light, time slows down. At the speed of light, time stops. If this is true then photons from 1 billions light years away would not exist in the present unless they stopped and remained stationary for 1 billion years after reaching earth...

Broken off from another thread: So here's a simple question for which the answer is not so simple using current theory: Do the photons from the CMBR exist free and independent of observation? Because some people say that photons are mediators of EM force but are otherwise abstractions. For...

Universe with only "e+", "e-", photons, and gravitation? In theory could we have a universe with only electrically charged spin 1/2 particles and antiparticles of mass m and electrical charge e and that interacted only gravitationally and electromagnetically? If so could we fine tune things...

Homework Statement When a certain light beam strikes a certain metal, 1 eV electrons are liberated. If the beam is replaced by one of half the original wavelength, 5 eV electrons are liberated. What is the energy of the photons in the original beam? Homework Equations Part of my...

What is the difference between the photon and the phonon ?

What's happen when a molecule or an atom is already in an excited electronic state and is hit from another photon? Example 1: my molecule absorbs a VIS photon (there's a time in which the molecule is an upper electronic state before the re-emission or etc. etc. process) what happen if another...

What would happen if energy would be applied to a photon in some direction? Since photons always travel at c, it shouldn't change their velocity no matter from what direction the energy would come, but what does applying energy do? I could imagine that if you applied energy from the front that...

According to Einstein's equation E=moc2, any object which has mass has energy, and, conversely, anything which has energy must also have mass. Then, why are photons, bosons and gluons said to be massless?

If I'm not mistaken, right (or left) circularly polarized light consists of photons with right-handed helicity (or left-handed). But what are the states of the photons in the (horizontally or vertically) linearly polarized light? Are all the photons in a superposition of two helicity...

It's my understanding that virtual photons are 'allowed' because their existence does not violate the uncertainty principle (the form using ΔE and ΔT). If this is the case though, how is the electromagnetic force transmitted over large distances?

Hello All, I am having a doubt. Generally, the electromagnetic radiation/photons are created when electrons accelerate in a field or fall from their excited state to normal state etc. Photons are waves of electrical & magnetic fields. Since, photons originate from electrons, shouldn't they...

Do photons experience time? If they move at the speed of light then special relativity states that they do not, but then does that mean they do not move forward in time which means the distance they travel is instantaneous (thus it is infinitely fast), which we know is not true (as they move at...

Is there any electromagnetic property of photons that make them attract towards each other?

How can one calculate the center of mass of a system made of two photons? I know that they have zero rest mass so the first intuition is to say that they do not have any center of mass. However, I read about something called center of momentum which is defined as a frame in which a moving...