The polarization of the total field changes with z. For example: we see that at z = 0 the field is linearly polarized along x ^ ^ ′ , at z = λ λ 8 the field has left circular polarization, at z = λ λ 4 the field is linearly polarized along y ^ ^ ′ , at z = 3 λ λ 8 the field has right circular polarization, and at z = λ λ 2 the field is again linearly polarized along x ^ ^ ′ .