EM wave polarization check
If we express the wave using two components: 


The wave is linearly polarized, if the phase angles of the two components are equal.(parallel vectors) 
The wave is circularly polarized, if phases are rotated by \$90^0\$ degrees with respect to each other and the  amplitudes are equal. (perpendicular vectors: zero dot product)
The wave is elliptically polarized, if phases are rotated by \$90^0\$ degrees with respect to each other and the  amplitudes are not equal.