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

For a plane electromagnetic wave,$E_x = 0$,$E_y = 2.5 \frac{N}{C} \cos \left[ (2\pi \times 10^6 \frac{rad}{s})t - (\pi \times 10^{-2} \frac{rad}{m})x \right]$,and $E_z = 0$. Which of the following is true?

In a plane $EM$ wave,the electric field oscillates sinusoidally at a frequency of $30 \text{ MHz}$ and amplitude $150 \text{ V/m}$. Identify the correct expression for $\vec{B}$ assuming the wave is propagating along the $x$-axis and the electric field is oscillating along the $y$-axis.

The unit of $\sqrt{\frac{2 I}{\varepsilon_0 c}}$ is
($I$: intensity of an electromagnetic wave,$c$: speed of light)

The energy density associated with the electric field $\overrightarrow{E}$ and magnetic field $\overrightarrow{B}$ of an electromagnetic wave in free space is given by ($\epsilon_0$ - permittivity of free space,$\mu_0$ - permeability of free space):

Write the equation for the energy density of electromagnetic waves.