All electromagnetic wave is transporting energy in the negative $$z$$ direction. At a certain point and certain time the direction of electric field of the wave is along positive $$y$$ direction. What will be the direction of the magnetic field of the wave at that point and instant?

An electromagnetic wave travels in the negative $$z$$-direction. At a point, $$\vec{E}$$ is along positive $$y$$-direction. Find the direction of $$\vec{B}$$.

Key Concept: For an EM wave, $$\vec{E} \times \vec{B}$$ gives the direction of propagation (Poynting vector direction).

Direction of propagation: $$-\hat{k}$$.

$$\vec{E}$$ direction: $$+\hat{j}$$.

We need $$\hat{j} \times \vec{B} \propto -\hat{k}$$.

If $$\vec{B} = B\hat{i}$$: $$\hat{j} \times \hat{i} = -\hat{k}$$ ✓

So $$\vec{B}$$ is along the positive $$x$$-direction.

The correct answer is Option A: $$\boxed{\text{Positive direction of } x}$$.

Expected is 17 (which doesn't match option numbering). Saving for review.