1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

What gives photons the energy to move at the speed they do

  1. Nov 10, 2009 #1
    I have a question...
    what gives photons the energy to move at the speed they do?
  2. jcsd
  3. Nov 10, 2009 #2


    User Avatar
    Science Advisor
    Homework Helper

    Re: photons...

    Photons always travel at the speed of light, regardless of their energy, because they are massless.
  4. Nov 10, 2009 #3
    Re: photons...

    A photon is pure kinetic energy. It alway travels at the speed of light, from the moment it is created. It's more accurate to say a photon has no rest mass than to say that it's massless.
  5. Nov 11, 2009 #4
    Re: photons...

    In wording that "what gives photons the energy", I wonder if the intent was to ask where the energy came from. There is always a source of the energy. If an electron in an atom drops to a lower energy state, for example, making a transition from the n=2 quantum number to the n=1 quantum number, it emits one photon. A nucleus that is in an excited state sometimes falls to a lower energy state, and gives off a gamma ray. An x-ray is given off when a moving electron hits a metal and loses its kinetic energy.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook