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 is 0.9726 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 is 6.4*10^-8. Then I use the energy density equation, which gives me 3*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 understand WHY! PLEASE HELP ME. Thankyou!!