Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Light speed in vacuum

  1. Aug 19, 2009 #1
    OK, I've been wondering, what's the significance of saying "speed of light in a vaccum" if lightspeed is a constant. Is the "vacuum" part even necessary?
     
  2. jcsd
  3. Aug 19, 2009 #2

    russ_watters

    User Avatar

    Staff: Mentor

    Except as a clarification that light only travels in a vacuum....light appears to travel slower through a medium but that is only because of occasional interactions between light and atoms.
     
  4. Aug 19, 2009 #3
    such as your frame of reference?
     
  5. Aug 19, 2009 #4

    russ_watters

    User Avatar

    Staff: Mentor

    Huh? That's not a complete sentence...
     
  6. Aug 20, 2009 #5

    Chronos

    User Avatar
    Science Advisor
    Gold Member

    Light travels unimpeded in a pure vacuum - where it achieves its maximum velocity. Photons traveling through a medium are absorbed then reemitted by atoms, which slows their journey. The amount of slowing depends on how long the photons are 'held' before reemitted, and the number of captures suffered before reaching an observer.
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook




Similar Discussions: Light speed in vacuum
  1. Speed of light. (Replies: 32)

  2. Speed of light (Replies: 17)

  3. Speed of light (Replies: 16)

Loading...