The polarization vector of an EM wave is a 2D vector e. We can take it to be in the x-y
plane when the wave propagates in the x direction. The intensity I (energy per time
per area) of the wave is proportional to the square magnitude of the vector I=e e,
which for reference we can take as I=1.
After passing through a polarizer, the polarization vector becomes f. a vector with
smaller or equal magnitude and of diƯerent direction. The vector is proportional to
the component of e along the polarization direction p (a unit vector).
We have f=p(e p) and the intensity after polarization is I=f f.
