Who first produced electromagnetic waves?

An electromagnetic wave of frequency $100 \text{ MHz}$ propagates through a medium of conductivity $\sigma = 10 \text{ mho/m}$. The ratio of maximum conducting current density to maximum displacement current density is . . . . . . . $\left[ \text{Take } \frac{1}{4 \pi \epsilon_0} = 9 \times 10^9 \text{ Nm}^2/\text{C}^2 \right]$

The voltage between the plates of a parallel plate capacitor of capacity $1 \ \mu F$ is changing at the rate of $4 \ V/s$. The displacement current in the capacitor is: (in $\mu A$)

Which of the following Maxwell's equations is valid for time-varying conditions but not valid for static conditions?

Give the equation that relates the speed of light $c$,the permeability of free space ${\mu _0}$,and the permittivity of free space ${\epsilon _0}$.

$AC$ voltage $V(t) = 20 \sin \omega t$ of frequency $50 \, Hz$ is applied to a parallel plate capacitor. The separation between the plates is $2 \, mm$ and the area is $1 \, m^2$. The amplitude of the oscillating displacement current for the applied $AC$ voltage is ...... $\mu A$.
[Take $\varepsilon_0 = 8.85 \times 10^{-12} \, F/m$]