In the propagation of electromagnetic waves,the angle between the direction of propagation and the plane of polarisation is (in $^{\circ}$)

Identify the correct statements from the following descriptions of various properties of electromagnetic waves.
$A$. In a plane electromagnetic wave,the electric field and magnetic field must be perpendicular to each other,and the direction of propagation of the wave should be along the electric field or magnetic field.
$B$. The energy in an electromagnetic wave is divided equally between the electric and magnetic fields.
$C$. Both the electric field and magnetic field are parallel to each other and perpendicular to the direction of propagation of the wave.
$D$. The electric field,magnetic field,and direction of propagation of the wave must be mutually perpendicular to each other.
$E$. The ratio of the amplitude of the magnetic field $(B_0)$ to the amplitude of the electric field $(E_0)$ is equal to the reciprocal of the speed of light $(1/c)$.
Choose the most appropriate answer from the options given below:

If the intensity of an electromagnetic wave is $0.02 \ W/m^2$ and its velocity in free space is $3 \times 10^8 \ m/s$,then the energy density of the radiation is ..... $J/m^3$.

$A$ cube of unit volume contains $35 \times 10^7$ photons of frequency $10^{15} \text{ Hz}$. If the energy of all the photons is viewed as the average energy being contained in the electromagnetic waves within the same volume,then the amplitude of the magnetic field is $\alpha \times 10^{-9} \text{ T}$. Taking permeability of free space $\mu_0 = 4\pi \times 10^{-7} \text{ Tm/A}$,Planck's constant $h = 6 \times 10^{-34} \text{ Js}$ and $\pi = \frac{22}{7}$,the value of $\alpha$ is $.....$

Write the characteristics of electromagnetic waves.

An electromagnetic wave of wavelength $2 \times 10^{-10} \,m$ passes from vacuum into a dielectric medium of relative permittivity $4$. Then its wavelength will be