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PHOTONS: Particle properties

  1. Jun 19, 2004 #1
    Do photons have an atomic nucleus with protons and neutrons and electrons? Does spin effect charge? Anything? Why do photons travel at c? Where do they get this power to travel at c from?
     
  2. jcsd
  3. Jun 19, 2004 #2

    chroot

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    Photons are fundamental particles; they do not have any internal composition, and cannot be broken down into smaller pieces.

    Spin is a different quantum number than is charge. They do not "affect" each other.

    Photons travel at c because they are massless. Maxwell's equations of electromagnetism describe self-perpetuating oscillations in the electromagnetic field, and these oscillations must propagate at a specific velocity, c, to be self-perpetuating.

    Photons do not need "power" to travel at c. Newton's first law indicates that an object in motion stays in motion unless acted upon by a force. A photon does not "propel" itself actively; it begins its life moving at c, and spends its entire life moving at c, until it hits something.

    - Warren
     
  4. Jun 19, 2004 #3
    Photons have enough energy to pass through a solid wall right?

    How about strings?
     
  5. Jun 19, 2004 #4

    chroot

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    Photons can pass through solid walls if they just happen to not interact with any of the atoms in the wall. The interaction of a photon with an atom is probabilistic; the best you can say is that a given photon has a certain chance of interacting with a given atom. If the wall is thick enough, the probability of interaction becomes very high, and very little light makes it through.

    Strings are also indivisible, but they can change characteristics like modes of vibration. I am frankly not well-versed on string theory, however, so perhaps someone else can add more.

    - Warren
     
  6. Jun 19, 2004 #5
    What happens exactly, when a photon interacts with the atoms in a given solid wall? Is there a virtual particle interaction of some sort when they interact? In what sense does a photon interact with atoms making up a wall? does it get absorbed by atoms (so that the atom becomes a high energy atom for a given period of time)?
    do photons have charge? I don't suppose so, since they aren't composed of any of the elementary particles.
     
  7. Jun 19, 2004 #6

    chroot

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    The photon interacts with the atom by giving an atom enough energy to change from one "orbit" to another. Basically, the photon gives its energy to the atom, exciting it. The energy doesn't disappear, it's just turned into heat.

    - Warren
     
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