Electromagnetic waves — UPSC CSE 2007 Physics PYQ

Consider superposition of two plane polarized electromagnetic waves: E_y = \hat{y} a \cos(kx - \omega t) \text{ and} E_z = \hat{z} b \cos(kx - \omega t + \phi) Discuss the conditions for the resultant wave to be left circularly and right circularly polarized adopting the convention as seen by an observer travelling with the wave.