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Q.
A plane electromagnetic wave propagating along $x$ direction can have the following pairs of $\vec{E}$ and $\vec{B}$
Electromagnetic Waves
Solution:
As electric and magnetic field vectors $\vec{E}$ and $\vec{B}$ are perpendicular to each other as well as perpendicular to the direction of propagation of electromagnetic wave. Hence options (a) and (b) are correct.