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Light and a photon

  1. Aug 2, 2010 #1
    Lately I've heard that when in transit, light is a wave. But when observed, its a light particle called photon.
    Anybody care to explain?

    Im quite a newbie on this subject, so dont be too rough on me.

    Thanks !
  2. jcsd
  3. Aug 2, 2010 #2


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  4. Aug 2, 2010 #3


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    What you CAN say about light is that it behaves like a wave but that its energy exists in specific 'Quanta' of energy; you can't have less than the appropriate quantum of energy for a particular wavelength. This means that, for any interaction (i.e. being produced or being detected) the interaction involves a specific (tiny) amount of energy. So people say that individual Photons interact with atoms. This doesn't actually imply that the photons are particles - just discrete packets of energy. Many phenomena in Physics can give the 'impression' that photons are like 'little bullets' but this model brings in the question of how big they would be and many other phenomena are very hard to explain in terms of particles. I have never heard a convincing answer to this so I avoid thinking of Photons as particles - just little dollops of energy. It avoids a lot of confusion.
    Most, if not all, phenomena can be 'explained' in just terms of waves in which the energy is quantised so don't feel bad about not 'getting' the particle idea.
  5. Aug 2, 2010 #4
    Thats how I've always pictured it. That light is a wave and that photon is a measurement of its energy. When I heard the sentence "Light is a wave in transit,"
    it confused the heck out of me.
  6. Aug 2, 2010 #5

    There is a complete lecture dealing with the double slit experiment and the quantum description of light by Richard P. Feynman... I highly recommend watching the lecture which will certainly clarify the issue for you...

    Good Luck :smile:
    Last edited by a moderator: Apr 25, 2017
  7. Aug 2, 2010 #6
    Is that video called "Probability and Uncertainty - The Quantum Mechanical View of Nature" ? Im asking because I dont have enough time to watch it right now, but just want to make sure its the right video.

    Last edited by a moderator: Apr 25, 2017
  8. Aug 3, 2010 #7
    Light is particle-like in that a packet will either be absorbed or not; it is all or nothing; it is observed to react or is misses.

    Light is wave-like because the formulas for computing where it winds up are very similar to the familiar equations of waves.
  9. Aug 4, 2010 #8
    Yeap... Thats it!
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