# EM waves; max value of electric field

Hello,
What is the max value of the eletric field at a distance 2.5m from 100W light bulb?

I have the formula E_o = [squ]2S/e_oc. This is what i have so far...
E_o = [squ]2(100W)/(8.85x10^-12C^2/Nm^2)(3x10^8m/s) = 274V/m.

My calculations are not right can someone help me with solving for this, please?

Thanks!
Dx

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Creator
Originally posted by Dx
Hello,
What is the max value of the eletric field at a distance 2.5m from 100W light bulb?

I have the formula E_o = [squ]2S/e_oc. This is what i have so far...
E_o = [squ]2(100W)/(8.85x10^-12C^2/Nm^2)(3x10^8m/s) = 274V/m.

My calculations are not right can someone help me with solving for this, please?

Thanks!
Dx

Wrong equation Dx.
S, the poynting vector, is not the power of the bulb. Rather, Power, P = S(4[pi]r^2). From this you can derive an eqn. which includes r.

Creator

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