The Poynting Vector ($\vec{S}$) represents the directional energy flux (power per unit area) of an EM wave. $\vec{S}=\frac{1}{{\mu }_0}(\vec{E}\times \vec{B})$

• The cross product direction indicates the direction of wave propagation.
• The magnitude $|S|$ gives the intensity of the wave in Watts per square meter ($W/m^2$).