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What is light?

  1. Apr 26, 2010 #1
    I know that light is electromagnetic radiation that behaves as a wave and as a photon and that it can travel through a vaccum, but what exactly is light?

    Is it just pure energy?
  2. jcsd
  3. Apr 26, 2010 #2


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    Oscillations in the electric and magnetic fields.

    Here's the canonical picture:
    http://www.mtholyoke.edu/~mlyount/MySites/Pictures/e_mag.JPG [Broken]
    Last edited by a moderator: May 4, 2017
  4. Apr 26, 2010 #3
    Electrons repel each other. So if you have an electron somewhere in space repelling another electron and that electron starts to move in any direction other than the direction it is pushing the other electron will move with it.

    If you push on a wall and you start accelerating upwards at the same time the wall will feel a force upward as well.

    This new component of force in the perpendicular direction is energy. It is the transfer of energy from one electron to the next in the same way you transfer energy to the wall you are pushing on while your accelerating.

    Electrons don't often accelerate off in one direction but rather oscillate back and forth the same as a pendulum would if you accelerated it for a moment and let go. This causes other surrounding electrons to oscillate as well.

    Everything is made up of electrons including our eyes, one way light effects something is by our eyes detecting specific oscillations (acceleration rates) that cause a signal to be sent to our brain. Another way is how high freq radiation can tear apart molecules in living things by accelerating the electrons too far away from the nucleus. This is also how the sun transfers energy to our world building molecular structures with potential energy for us to eat.

    The original pushing force is simply the electric force, the force is conserved here and this force is not part of the energy measured in light, only the perpendicular forces.
  5. Apr 26, 2010 #4
    Light is the stuff you see when you open your eyes.

    It's not really productive to ask questions like this. If I told you light was made of up a string of marions, you wouldn't understand light any better than you did before I explained it. What you want to know is not what light is, but rather, how light behaves.

    From there, you can say light behaves like a particle, like a wave, like a string of marions (provided you knew how a marion behaved), and you'll know what light is. How the universe represents light is unimportant, because you know whatever material nature chose to make light, it always acts the way science has discovered it to.
  6. Apr 28, 2010 #5
    lost - by what mechanism do electrons repel each other? if each electron moves, there must be energy somehow imparted to them - where does that energy come from, and how is it transfered? i think it is clear that without some fundamental understanding of what a field is, we cannot understand what anything is, but, as mentioned above, can only talk about how things behave...
  7. Apr 28, 2010 #6
    This is a different question. What is the electric field? This is a field theory question and is way beyond my knowledge. The maxwell equations where derived from experimentation and so do not explain the mechanism of the electric field.

    If electron1 pushes electron2 some distance away from it's location, electron1 moves exactly the same distance in the opposite direction. So from the right perspective nothing is really happening.
  8. Apr 28, 2010 #7
    Light is photons. Quantum objects that obey laws of motion characteristic of quantum mechanics, in which the position and the momentum can't both have precise physical values. The calculations to determine where a photon ends up involves the same math that work for classical waves, so it seems "wave-like" when taken in bulk quantities.

    Photons are elementary things (though perhaps a deeper theory will come along some day), so "just are" as far as we know. They are not made out of smaller components, but behave similarly to other kinds of quantum particles in a family way.

    Photons can have an effect on electrons. That's part of what they are.

    Does that help?
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