An E.M. wave is propagating along the +z-axis. The electric and the magnetic field in it can be represented by

The electromagnetic wave is propagating along the +z axis. Since the electric and magnetic fields are perpendicular to each other and also perpendicular to the direction of propagation of the wave.Also, E→×B→ gives the direction of wave propagation.E→=E0i^,B=B0j^(∵i^×j^=k^)