The electric field for an electromagnetic wave in free space is $E = i 30 \cos (k z - 5 \times 10^8 t)$,where the magnitude of $E$ is in $V/m$. The magnitude of the wave vector $k$ is (velocity of electromagnetic wave in free space $= 3 \times 10^8 \ m/s$).

$A$ 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:

In the propagation of electromagnetic waves,the angle between the direction of propagation and the plane of polarisation is......$^o$.

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.

What is the range of frequency of $EM$ waves that are reflected back by the ionosphere?

The radiation energy emitted per second by a point source is $100 \,W$. If the efficiency of the source is $4 \%$, then the rms value of the electric field at a distance of $2 \,m$ is [use $\frac{1}{4 \pi \varepsilon_0}=9 \times 10^9$ in $SI$ units].