I found in my textbook that
Oscillation of light wave mainly represents the periodic change of electric field $ \vec E$ as contribution of $\vec E$ is the most significant here which creates optical sensation to our eyes.. The direction of the electric vector can be in any direction among all directions on a plane perpendicular to the direction of wave propagation named as electromagnetic wave. But at any given point in time, there will be only one resultant magnetic field.
But according to the figure, I see two fields symmetric here. And 'Ampere's Law' roughly states that 'a changing electric field creates a magnetic field'. Then how can in a particular moment, magnetic field be in any one arbitrary direction?