 Now suppose a linearly polarized wave is incident on the crystal.This wave can be written as
where the "f" and "s" axes are the quarter-wave plate's fast and slow axes, respectively, the wave propagates along the "z" axis, and "Ef" and "Es" are real.The effect of the quarter-wave plate is to introduce a phase shift term e"i"Γ =e"i"π/2 = "i" between the "f" and "s" components of the wave, so that upon exiting the crystal the wave is now given by
The wave is now elliptically polarized.