The epsilon symbol (##\epsilon##) stands for "emf" or ElectroMotive Force. I think it's a bit of a technicality to name voltage sources like batteries with ##\epsilon## while potential difference generated across other components are labeled as Voltage (V).
Thank you very much for the explanation! That seems to solve it perfectly.
The wavenumber by spherical coordinates looks like a super useful formulae , do you mind giving me it's name or linking me to some reference for me to read up more on it? The bit about phase difference between two...
Although problem says sketch, what I really want is the formulae by θ for the radiation. After trying this for a while I cheated and looked at the solution. I still can't figure out the steps on how to get to the solution. the answer is:
What I tried:
I'll assume that the intensity from a...