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Photons and matter

  1. Apr 22, 2014 #1

    Why do photons not pass through matter like neutrinos since they have no charge. What are they interacting with when they are stopped by matter?

  2. jcsd
  3. Apr 22, 2014 #2


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    Staff: Mentor

    They have no charge, but they interact electromagnetically - in fact, that's about the only thing they do.
  4. Apr 22, 2014 #3
    as above photons, interact electromagnetically with two very important particles that create up 'matter' in the universe protons and electrons. these are charged. Neutrinos have an extremely low to nil mass and only interact with matter via the weak force which has a very small range.
  5. Apr 22, 2014 #4
    If they have no charge how is it that they interact with the electromagnetic forces?
  6. Apr 22, 2014 #5
    light is electromagnetic radiation. when photons makes contact with matter it transfers its energy to the particles in the matter. There is a finite probability of a photon passing through matter, this is all dependent on characteristics of the photons and matter its passing/making contact with, e.g. type of matter(more densely packed atoms have higher chance to come in contact with photons. And or photon energy.

    A usual/interesting thing for you to research on maybe electron energy levels and spectroscopy.

    Also research fundamentally why we call light "Electromagnetic Radiation"
  7. Apr 22, 2014 #6


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    Staff: Mentor

    They are the electromagnetic force, in the sense that they mediate the electromagnetic force between two charged particles via exchange of virtual photons. The two charged particles don't change their charge in the process, so the photon itself must not have any charge.
  8. Apr 23, 2014 #7


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    From the wording you are using, it's possible that you are trying to think in terms of photons being 'particles' in the conventional sense of the word, rather than quantum particles. Personally, I think it was an unfortunate choice of word for the Quantum of EM Energy.
  9. Apr 23, 2014 #8


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    Photons are not simply little particles with zero electric charge. They are the quanta of energy that an EM wave interacts with matter by. In other words, an EM wave, which is an oscillation in the electric and magnetic fields, transfers energy only in discrete amounts. The oscillations exert an alternating electric force on charged particles. In fact, the oscillations themselves are in the vectors that represent the direction and magnitude of the force on charged particles.
  10. Apr 23, 2014 #9
    Rather than thinking that charges interact with charges, know that charges can only interact with the electromagnetic field. When someone says that charges interact with charges it is implied or taken for granted that they do so via the electromagnetic field.
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