Select the incorrect statement regarding electromagnetic waves.

The electric field of an electromagnetic wave in free space is $\overrightarrow{E}=57 \cos \left[7.5 \times 10^6 t-5 \times 10^{-3}(3 x+4 y)\right]\ (4 \hat{i}-3 \hat{j})\ N/C$. The associated magnetic field in Tesla is

$A$ sky wave with a frequency of $55 \text{ MHz}$ is incident on the $D$-region of the ionosphere at an angle of $45^\circ$. What is the angle of refraction? (The electron density in the $D$-region is $400 \text{ electrons/cm}^3$).

If the relative permeability and dielectric constant of a medium are $\mu_r$ and $K$ respectively,then the refractive index $n$ of the medium is:

In an electromagnetic wave,at an instant and at a particular position,the electric field is along the negative $z$-axis and the magnetic field is along the positive $x$-axis. Then the direction of propagation of the electromagnetic wave is

The ratio of the amplitude of the magnetic field to the amplitude of the electric field for an electromagnetic wave propagating in vacuum is equal to: