Which scientist experimentally proved the existence of electromagnetic waves?

Maxwell's equations describe the fundamental laws of

$A$ charged particle oscillates about its mean equilibrium position with a frequency of $8 \times 10^9 \text{ Hz}$. What is the frequency of the electromagnetic waves produced by the oscillator?

Suppose that the electric flux inside a parallel plate capacitor changes at a rate of $7 \times 10^{14} \text{ V} \cdot \text{m/s}$. If the area of the plates is $1 \text{ m}^2$,calculate the magnetic field $B$ at a distance $r = 0.1 \text{ m}$ from the axis of the capacitor. (Given: $\varepsilon_0 = 8.85 \times 10^{-12} \text{ F/m}$,$\mu_0 = 4\pi \times 10^{-7} \text{ T} \cdot \text{m/A}$)

$A$ parallel plate capacitor with plate area $A$ and separation between the plates $d$ is charged by a constant current $i$. Consider a plane surface of area $A/2$ parallel to the plates and drawn symmetrically between the plates. The displacement current through this area will be:

At what rate must the potential difference between the plates of a capacitor be changed to set up a displacement current of $1 \, A$ in a capacitor of $2 \, \mu F$?