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Homework Help: What is the electric field amplitude 2m from the source

  1. Jan 19, 2007 #1
    1. The problem statement, all variables and given/known data
    A 60 W monochromatic point source is radiating equally in all diresctions in a vacum. What is the electric field amplitude 2m from the source.

    2. Relevant equations
    Intensity=Power/(4*Pi*r^2), Intensity proportional to square Amplitude

    3. The attempt at a solution
    I=1.19 Wm-2 what happens next?
  2. jcsd
  3. Jan 21, 2007 #2

    Meir Achuz

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    Use I=(1/2)\epsilonzero c E^2.
  4. Jan 25, 2007 #3
    Desperate semi related question. If you have a graph of log intensity against log of (voltage across an LDR in a potential divider circuit)
    how do you explain the relationship if your resultant is a straight line of -1.7 obviously in the form of y=mx+c
    Log(y)= nlog(x) + logm where y is intensity and x is voltage n being -1.7 and logm being y intercept.
    im trying to explain the relationship between the two quantities and ... im stuck if anyone can help me i would very much appreciate it...
  5. Jan 26, 2007 #4


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    Welcome to PF, hopeless blonde. In future, however, please don't hijack another person's thread with your own question-- instead, start a new thread in the relevant homework section.

    With regard to your question, you have an equation of the form logy=nlogx+logm. Now, nlogx can be expressed as log(xn). Do you know a rule for loga+logb?
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