Question

Determine the direction of Poynting vector for an electromagnetic wave when its electric field component is oscillating in the $+y$ direction and the magnetic field component oscillates in the $-z$ direction.

• A. $-\hat{i}$
• B. $\hat{i}$
• C. $\hat{j}$
• D. $-\hat{j}$

Answer 1

The correct option is A $-\hat{i}$

It is given that, the electric field is along $+y$ axis direction while the magnetic field is along $-z$ axis direction.
Then, using Poynting vector formula we have,

$\hat{S}=\hat{E}\times \hat{B}$

i.e. $\hat{S}=\hat{j}\times -\hat{k}=-(\hat{j}\times \hat{k})$

So, the resultant direction is $-\hat{i}$