\(\vec{s}=\frac{\vec{E} \times \vec{B}}{\mu_{o}}\)

-wherein

It is total energy flowing perpendicularly per second per unit area into the surface in free space.

\(\vec{E} \times \vec{B}\) should give a direction of wave propagation

\(\Rightarrow \vec{E} \times \vec{B} \| \frac{\hat{i}+\hat{j}}{\sqrt{2}}\)

option \((1) \hat{k} \times\left(\frac{\hat{i}+\hat{j}}{\sqrt{2}}\right)=\frac{\hat{j}-\hat{i}}{\sqrt{2}} \| \frac{\hat{i}-\hat{j}}{\sqrt{2}}\)

option \(( 2)\) and \(( 4)\) does not satisfy this wave propagation vector should be

\(\operatorname{along} \frac{\hat{i}+\hat{j}}{\sqrt{2}}\)