ABSTRACT
The macroscopic electromagnetic description of matter is given by Maxwel l ' s
equations. In this chapter the meaning of the electric and magnetic fields as
well as the other variables that enter the Maxwel l equations is examined starting
from a derivation of these equations. Underlying the Maxwel l equations are the
Maxwel l -Lorentz equations, which describe a material complete with every wiggle
produced by the microscopic structure. In essence, the Maxwel l equations in
matter are just the result of smoothing out the set of Maxwel l -Lorentz equations.
