How are radio waves produced?

$A$ parallel plate capacitor is charged to $60\,\mu C$. Due to a radioactive source,the plate loses charge at the rate of $1.8 \times 10^{-8}\, C/s$. The magnitude of the displacement current is:

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 . . . . . . . $\left[ \text{Take } \frac{1}{4 \pi \epsilon_0} = 9 \times 10^9 \text{ Nm}^2/\text{C}^2 \right]$

When a displacement current $i_d$ flows in the region between the two plates of a capacitor,the charge on the capacitor is:

Who first produced electromagnetic waves?

Displacement current is given by