- #1
MadMax
- 99
- 0
Why does the Lagrangian density for the EM field in a dielectric medium take the form [tex]d^3 \bf x \left[ \epsilon \bf E^2 - \bf B^2 \right][/tex]? I can see that the expression for Lagrangian density has units of energy per unit volume as you would expect but that's about it. Much appreciated.