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Homework Help: Energy carried by Electromagnetic Waves

  1. Oct 31, 2008 #1
    1. The problem statement, all variables and given/known data
    An industrial laser is used to burn a hole through a piece of metal. The average density of the light is S = 1.24E9 W/m2. What is the rms value of each of the following fields in the electromagnetic wave emitted by the laser?

    2. Relevant equations
    S = ceoE2
    S = (c/uo)B2
    S is average density and E,B are rms values.

    3. The attempt at a solution
    Solving for E:
    sqrt(S/ceo) = E
    sqrt(1.24E9/(3e8 x 8.85E-12)) = E = 683405.7 N/C

    Solving for B:
    E = cB
    E/C = B
    4.67E11/3E8 = .00228T

    I have 5 tries to get this homework right and I'm down to my last one. I want to make sure I'm not leaving anything out this time. Any help is appreciated!
  2. jcsd
  3. Nov 1, 2008 #2


    User Avatar
    Staff Emeritus
    Science Advisor
    Homework Helper

    Looks good. You might need to watch the significant figures on the answer for E, they checked for that.
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