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

Speed of light question

  1. Dec 19, 2006 #1
    this isn't actually homework but i fear it is too simple to put in any of the other forums :redface:
    why is it that you can calculate the speed of light by (permettivity*permeability of free space)^-0.5
    i can't seem to find it in any of my textbooks, but my physics teacher told me it was a standard proof thing...
  2. jcsd
  3. Dec 19, 2006 #2
    you can derive it using maxwell's equations
  4. Dec 19, 2006 #3


    User Avatar

    Staff: Mentor

    More specifically, if you use Maxwell's equations to derive the wave equation for E or B, you get something that looks just like the standard differential wave equation, with [itex]1/\sqrt{\epsilon_0 \mu_0}[/itex] where the wave speed should be.
  5. Dec 19, 2006 #4
    is it something doable by an A level student? cos i've heard about maxwell's equations but it's not on the syllabus...
    also, what are E and B?
  6. Dec 19, 2006 #5
    E = electric field
    B = magnetic field

    how much calculus have you done??
  7. Dec 19, 2006 #6
    int. by parts, substitution, integrating trig, first order differential equations
  8. Dec 19, 2006 #7


    User Avatar

    Staff: Mentor

    Sounds like you have a lot of the background, as long as you've had some vectors mixed in with the calculus. I googled something like maxwell equations derivation wave equation, and got lots of good hits. Here's one of the first hits on the list:


    EDIT -- Also, if you have access to a technical library, just check out some of the books on Electromagnetics. Most will have the derivation.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook