Answer
As the EM wave travels in the +x-direction, the magnetic field oscillates horizontally along the z-axis, and the electric field oscillates vertically along the y-axis.
Work Step by Step
As the EM wave travels in the +x-direction, the magnetic field oscillates horizontally along the z-axis. The electric field is perpendicular to the magnetic field and perpendicular to the direction of motion of the wave. Therefore, the electric field oscillates vertically along the y-axis.
