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Light intensity in matter

  1. Apr 22, 2015 #1
    1. The problem statement, all variables and given/known data
    An electromagnetic wave with frequency 65.0Hz travels in an insulating magnetic material that has dielectric constant 3.64 and relative permeability 5.18 at this frequency. The electric field has amplitude 7.20×10−3V/m.

    What is the intensity of the wave?

    2. Relevant equations
    I = S average = 1/2 ε0 c Emax2

    3. The attempt at a solution
    the above equation is what I only have from my textbook, and it is for vacuum case. However, in the question, it has dielectric constant and relative permeability. I tried changing c into the light speed in the medium, not correct. I tried using equation from wiki, that is, times refractive index in the above equation, doesn't work. I tried simply ignore the refractive index problem, and doesn't work.
     
  2. jcsd
  3. Apr 23, 2015 #2

    Simon Bridge

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    Please show your working.
    How do you know "it didn't work"?

    You book should have shown you a derivation for the formula it gave you... check that you are accounting for all the assumptions correctly.
    Your book should include some text about how EM fields are different in a medium.
    Have a go deriving the formula for intensity in a magnetic medium.
     
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