How Do I Determine the Polarization State and Azimuthal Angle of a Wave?

[roam]

Homework Statement

Determine the state of polarization of the following wave and its azimuthal angle:

$E= \sqrt{3} E_0 \cos(kz-\omega t) \hat{x} + E_0 \cos(kz- \omega t + \pi) \hat{y}$

The Attempt at a Solution

How do I calculate the azimuthal angle?

My textbook only says: "the azimuthal angle is defined as the angle between the plane of vibration and the plane of incidence". Since no diagrams are provided I'm not sure if I understand it correctly... Is this the angle it makes with the x-axis if it is linearly polarized (or if elliptically polarized, the angle of the major axis with respect to the x-axis)?

I think the state of polarization is linearly polarized since E_y lags E_x by π, right? Also the E_x has a greater amplitude than E_y by a factor of √3.

Any help is greatly appreciated.

 

[UltrafastPED]

For definitions see http://en.wikipedia.org/wiki/Plane_of_incidence

 

[roam]

For definitions see http://en.wikipedia.org/wiki/Plane_of_incidence

It doesn't give the definition of the "azimuthal angle". I believe it's the angle θ I've marked in the attached diagram. How can it be calculated?

 

[roam]

How do I calculate azimuthal angle for this wave?

I know it's not 45° because $E_x \neq E_y$. Is it valid to use trig like this:

$\tan \theta = \frac{E_y}{E_x} = \frac{E_0}{\sqrt{3} E_0} \implies \theta = 30°$