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

For an electromagnetic wave,the electric field is given by $E_x = 36 \sin(1.20 \times 10^7 z - 3.6 \times 10^{15} t) \ V/m$. What is the intensity of the electric field in $W/m^2$?

Electromagnetic waves are:

An electromagnetic wave has an electric field given by the expression (in Cartesian coordinates) $\vec E(x,t) = 6.0\,\cos(1 \times 10^7x - 3 \times 10^{15}t)\hat z$. What is the direction of the magnetic field at time $t = 0$ and position $x = 0$?

$A$ plane electromagnetic wave of frequency $20 \ MHz$ travels in free space along the $+x$ direction. At a particular point in space and time, the electric field vector of the wave is $E_y = 9.3 \ Vm^{-1}$. Then, the magnetic field vector of the wave at that point is:

Pick out the statement which is not true.