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Energy per unit area of EM wave

  • Thread starter x^2
  • Start date
  • #1
x^2
21
1

Homework Statement



The E field in an EM wave has a peak of 22.8 mV/m. What is the average rate at which this wave carries energy across unit area per unit time?

Homework Equations



S = e_0*c*E^2


The Attempt at a Solution



where e_0 = 8.85*10^-12
c = 3*10^8
E = 0.0228 V/m

S = (8.85E-12)*(3*10^8)*(0.0228)^2 = 1.38017E-6 W/m^2

Hello,

I trying finding the Poynting vector S using the equation e_0*c*E^2 as I have all the needed values. This produces an answer of 1.380E-6 W/m^2 which was incorrect. Where did I go wrong?

Thanks,
x^2
 

Answers and Replies

  • #2
x^2
21
1
Got it... I have to divide the peak of the E field by Sqrt(2) to get the RMS or the average value so I can find the average energy.

Thanks for such a great resource!
x^2
 

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