Which one of the following statements is correct?

If $E$ and $H$ represent the intensity of the electric field and the magnetising field respectively,then the unit of $E/H$ will be:

The electric field part of an electromagnetic wave in vacuum is
$E = 3.1 \, N C^{-1} \cos [ (1.8 \, rad \, m^{-1}) y + (5.4 \times 10^8 \, rad \, s^{-1}) t ] \hat{i}$
The wavelength of this part of the electromagnetic wave is ...... $m$.

$A$ plane electromagnetic wave travelling along the $X-$ direction has a wavelength of $3\, mm$. The variation in the electric field occurs in the $Y-$ direction with an amplitude of $66\, Vm^{-1}$. The equations for the electric and magnetic fields as a function of $x$ and $t$ are respectively:

Electromagnetic waves consist of periodically oscillating electric and magnetic vectors:

For electromagnetic waves,the phase difference between the $\vec{E}$ and $\vec{B}$ vectors (for the region far from the source) is......