(adsbygoogle = window.adsbygoogle || []).push({}); Energy Carried by Electromagnetic Waves- why is it wrong???

Hi! I have this homework problem that I just don't understand why it's wrong.

A monochromatic light source emits 110 W of electromagnetic power uniformly in all directions.

(a) Calculate the average electric-field energy density 3.00 m from the source.

(b) Calculate the average magnetic-field energy density at the same distance from the source.

(c) Find the wave intensity at this location.

First of all, I know that(a)and(b)will be the same. I have also calculate part(c), which is correct, and it is0.9726 W/m^2.

I have used various equations that would work for this type of problems.

1. The Sav, or average Poynting vector, in terms of the magnetic and electric field. I always get the same answer, which is6.4*10^-8. Then I use the energy density equation, which gives me3*10^-9.

2. I use Sav=cu....since I have Sav, and I know c, then it seemed logical to use this. My answer is the same,3*10^-9.

But its WRONG, and I don't understandWHY! PLEASE HELP ME.

Thankyou!!

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# Homework Help: Energy Carried by Electromagnetic Waves- why is it wrong?

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