What is Photon mass: Definition and 27 Discussions

The photon (Greek: φῶς, phōs, light) is a type of elementary particle. It is the quantum of the electromagnetic field including electromagnetic radiation such as light and radio waves, and the force carrier for the electromagnetic force. Photons are massless, so they always move at the speed of light in vacuum, 299792458 m/s (or about 186,282 mi/s). The photon belongs to the class of bosons.
Like all elementary particles, photons are currently best explained by quantum mechanics and exhibit wave–particle duality, their behavior featuring properties of both waves and particles. The modern photon concept originated during the first two decades of the 20th century with the work of Albert Einstein, who built upon the research of Max Planck. While trying to explain how matter and electromagnetic radiation could be in thermal equilibrium with one another, Planck proposed that the energy stored within a material object should be regarded as composed of an integer number of discrete, equal-sized parts. To explain the photoelectric effect, Einstein introduced the idea that light itself is made of discrete units of energy. In 1926, Gilbert N. Lewis popularized the term photon for these energy units. Subsequently, many other experiments validated Einstein's approach.In the Standard Model of particle physics, photons and other elementary particles are described as a necessary consequence of physical laws having a certain symmetry at every point in spacetime. The intrinsic properties of particles, such as charge, mass, and spin, are determined by this gauge symmetry. The photon concept has led to momentous advances in experimental and theoretical physics, including lasers, Bose–Einstein condensation, quantum field theory, and the probabilistic interpretation of quantum mechanics. It has been applied to photochemistry, high-resolution microscopy, and measurements of molecular distances. Recently, photons have been studied as elements of quantum computers, and for applications in optical imaging and optical communication such as quantum cryptography.

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  1. Pradyuman

    A Why can't we say that photon has very very small mass?

    Any wave mass term decays, similarly if I want to explain redshift by considering massive photon, how much should be the mass? Is it less than today's upper limit. Solution of wave equation ##□ϕ=0## gives a wave that doesn't disperse over time. But wave solution of the form ##(□+m^2)ϕ=0## has...
  2. virgil1612

    B Relativistic Photon Mass: Can It Exist?

    Photons have 0 rest mass. But could I talk about relativistic, or dynamic photon mass, that would be the solution of hf = mc^2 ? The relativistic mass would be m = m0/sqrt(1-v^2/c^2), where m0 is the rest mass, so 0, and v = c, so the denominator is also 0. The previous equations would give 0/0...
  3. M

    A Does Dim Reg really avoid a photon mass?

    In the loop integral for the one-loop correction to the photon propagator in QED, the dominant term, after Wick rotation and angular averaging, has the form (omitting uninteresting factors) $$(1-2/d) e^2 \eta^{\mu\nu}\int_0^\infty \frac{p^{d+1}}{(p^2+\Delta)^2}dp,$$ where ##p## is the absolute...
  4. SamRoss

    I Still have questions about photon mass

    Just read the FAQ post "Do photons have mass?" and I'm still confused. The post says that all of the photon's energy is in the pc term of the energy-momentum equation. (1) But isn't p equal to mv, implying there is mass? (2) The post also says there is no inconsistency with E=mc^2 but doesn't...
  5. Warda Anis

    Perturbation for Yukawa Potential

    Homework Statement The photon is normally assumed to have zero rest mass. If the photon did have a tiny mass, this would alter the potential energy the electron feels in the hydrogen atom (due to the Coulomb interaction with the proton). The potential then becomes yukawa potential...
  6. Bolhuso

    I Use of polarization to experimentally check photon mass?

    Hi all! I've checked Wikipedia and a related thread regarding experimentally measuring an upper limit for the photon rest mass: https://en.wikipedia.org/wiki/Photon#Experimental_checks_on_photon_mass https://www.physicsforums.com/threads/photon-rest-mass-0-wasnt-proven-experimentally.792583/ I...
  7. P

    I Experimental check of photon mass and Coulomb's law

    Despite some effort I still don't understand how Coulombs law can be used for experimental search for mass of photon. From wikipedia: If a photon did have non-zero mass, there would be other effects as well. Coulomb's law would be modified and the electromagnetic field would have an extra...
  8. DaTario

    Presumed mass content of photon as gravitational source

    Hello, I have read some of the posts which discuss the meaning and mistakes involving the equation: ## m_0 = \frac{h f }{c^2}.## My question has to do with gravitation. I would like to know if it is correct to associate to a photon with frequency f, crossing a region near a mass M, a...
  9. Garlic

    I Exploring Photon Mass: Is It Zero or Relativistic?

    Hello everyone, I know that the photon has zero rest mass and I know that otherwise the relativistic mass formula would not make sense. When I searched for an answer to the question "how can a particle have zero mass and still possesses energy if E=mc^2" I got an answer saying the mass energy...
  10. akashpandey

    About light, photon mass and E=mc^2

    Light is form of energy. Accordingto einstine theory if we concentrate the energy of light we have to get mass of light. But their is no mass of light. Acc.to E⇒mc2.
  11. A

    E=MC^2 Explained: Photon Mass & Energy

    A photon has “zero” rest mass, but it does have Energy, But with zero Mass , E=MC^2 yields E=0 I am confused !
  12. M

    Exploring the Possibility of Photon Mass

    Lately, I have been giving a lot of thought to whether or not photons would have mass or not. I know most on here an on other sites say that they do not have mass, but I think differently. If light has no mass, then theoretically, it shouldn't have any speed limit (186,282 mi/sec) because...
  13. B

    Photon mass - clarification request

    Am I correct in thinking it is currently believed that a single photon at rest has no mass a single photon in motion does have mass ?
  14. C

    Does the Ward identity rescue a zero photon mass?

    In Peskin at page 248 he finds that if he calculates the vacuum polarization that $$\Pi(q)^{\mu \nu} \propto g^{\mu \nu}\Lambda^2$$ a result which violates the Ward identity and would cause a non-zero photon mass $$M \propto \Lambda$$. But as Peskin states, the proof of the Ward identity...
  15. B

    Best attempts at measuring photon mass?

    What are the most recent or most accurate attempts at measuring photon mass? Additionally, what are the upper limits, uncertainty or error associated with those measurements?
  16. umair20

    Why Photon Mass is Zero: Proving it with Relativity Theory

    why rest mass of photon is zero? how to prove it by m=m'/√(1-v^2/c^2)?
  17. bcrowell

    Photon Mass: Empirical Limits & Implications

    We used to think neutrinos were massless, and therefore traveled at c. Now we know that at least some types of neutrinos have mass, and travel at less than c. What about the photon? Section I.2 of Jackson has a description of the empirical limits on the mass of the photon. (This is the...
  18. F

    Upper Bound of Photon Mass - Sources & Review Articles

    Can you tell me the best known upper bound for the photon mass? If possible also provide a link to the source or to a review article on the subject. Thanks much.:smile:
  19. D

    Does the Photon Mass of the Universe Add Up?

    I know that Photons have no mass at all. Although I read it was something insanely small like 1.1×10−52 kg. So because it still has some small mass, and the fact that there are so many photons. If it was possible to get all the photons in the Universe in one spot say the size of a cup...
  20. D

    Photon Inertial Mass: Zero Rest Mass?

    I'm still struggling with the concept of a mass of a photon. I understand that photons have momentum because of their inertial mass...m = p/v. This makes sense to me but what does it mean to say they have zero 'rest mass'. If they have momentum at some time t, and thus inertial mass at that...
  21. S

    .Showing Gauss' Law is False with Photon Mass "m"

    hi I have this question, I need your help: If the photon had mass "m" , show that the Gauss' law would no longer be true. Note that the electric poential for a point charge would then have a form V(r) = e/r exp ( -mc/h * r ) Thank you
  22. M

    Does the Neutrino Scattering Experiment Suggest a Photon Mass?

    Yukawa potential leads to an expression for the amplitude of . \frac{4\pi^2\hbar^2}{q^2 + m^2c^2} m = mass of exchange boson. An experiment was performed scattering high energy neutrinos off electrons. No change in the cross-section was observed as the momentum...
  23. B

    Exploring the Mystery of Photon Mass Zero: Fact or Fiction?

    Photon Mass Zero? Ok right to the point, I've learned that a Photon since it is moving at c has a mass zero, but yet I've also heard that with a sensitive enough scale, that you can measure the force of sunlight or other light as photons...very small force, but still a force A measureable...
  24. B

    Photon Mass: Is Student Learning Misleading?

    Is the student not correctly taught if the intructor says: the photon has no rest mass but it has a m=E/cc dynamic mass? Could such a statement have missleading consequences?
  25. M

    Exploring Modern Physics: Wave-Particle Duality & Photon Mass

    I was reading in one of my books today. It brought up an answered that I had when I was talking Modern PHysics over a year ago. Sadly our curriculum didn't really allow for us to do modern physics but our class flew through all the old physics for grade 12. Basically I had read a lot of...
  26. I

    What is Rest Mass? Explaining Photon Mass Zero

    what is rest mass? why does a photon have rest mass zero? :uhh:
  27. F

    Does Light Have Mass? Flannigan's Take on Photon Mass

    [SOLVED] Flannigan on Photon Mass I'm sorry...gotta weigh in here. Light does have mass of sorts depending on what slant you take on it. Remember your theory from school. Floyd
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