Answer
(a) The wave is traveling in the +y-direction.
(b) $B_x = \frac{E_m}{c}~sin~(ky+\omega t+\frac{\pi}{6})$
$B_y = 0$
$B_z = 0$
Work Step by Step
(a) From the term $ky-\omega t$, we can see that the wave is traveling in the +y-direction.
(b) Since the direction of propagation is determined by the cross-product $E\times B$, by the right-hand rule, the magnetic field must be pointing in the +x-direction at y = 0 and t = 0. Note that $(+z)\times (+x) = +y$
We can find the components of the magnetic field of this wave:
$B_x = \frac{E_m}{c}~sin~(ky+\omega t+\frac{\pi}{6})$
$B_y = 0$
$B_z = 0$
