Jagdish Chandra Bose produced electromagnetic waves of which range?

$A$ flood light is covered with a filter that transmits red light. The electric field of the emerging beam is represented by a sinusoidal plane wave
$E_x=36\,\sin\,(1.20 \times 10^7z -3.6 \times 10^{15}\,t)\,V/m$
The average intensity of the beam will be.....$W/m^2$

The speed of electromagnetic waves in a medium is $1.5 \times 10^8 \ m/s$. If the relative permittivity of that medium is $2$,then its magnetic susceptibility is (speed of light in vacuum is $3 \times 10^8 \ m/s$).

To heat the food containing water,the frequency of the microwaves used in a microwave oven is

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.

An electromagnetic wave of frequency $\nu = 3.0\,MHz$ passes from vacuum into a dielectric medium with permittivity $\varepsilon = 4.0\varepsilon_0$. Then