The refractive index of the ionosphere is

Which of the following is/are the property/properties of a monochromatic electromagnetic wave propagating in the free space?
$1$. Electric and magnetic fields will have a phase difference $\frac{\pi}{2}$.
$2$. The energy of the wave is distributed equally between electric and magnetic fields.
$3$. The pressure exerted by the wave is the product of its speed and energy density.
$4$. The speed of the wave is equal to the ratio of the magnetic field to the electric field.

Which of the following is $NOT$ true for electromagnetic waves?

If the average power per unit area delivered by an electromagnetic wave is $9240 \ W \ m^{-2}$,then the amplitude of the oscillating magnetic field in the $EM$ wave is: (in $\mu T$)

Consider an electromagnetic wave propagating in a vacuum. Choose the correct statement.

Long-distance radio broadcasting uses which of the following waves?