A linearly polarised electromagnetic wave in vacuum is $E=3.1\cos \left[\left(1.8\right)z-\left(5.4\times {10}^6\right)t\right]\hat{\mathrm{i}} \mathrm{N} {\mathrm{C}}^{-1}$ is incident normally on a perfectly reflecting wall at $z=a$. Choose the correct option.

A plane electromagnetic wave of frequency $500 \mathrm{MHz}$ is traveling in a vacuum along the $y-$direction. At a particular point in space and time, $\overrightarrow{B}=8.0\times {10}^{-8}\hat{\mathrm{z}} \mathrm{T}$. The value of the electric field at this point is:(speed of light $=3\times {10}^8{ \mathrm{ms}}^{-1}$) $\hat{\mathrm{x}},\hat{\mathrm{y}},\hat{\mathrm{z}}$ are unit vectors along $x,y$ and $z$ direction.

If $2.5\times {10}^{-6} \mathrm{N}$ average force is exerted by a light wave on a non-reflecting surface of $30{ \mathrm{cm}}^2$ area during $40 \min$ of time span, the energy flux of light just before it falls on the surface is _______ $\mathrm{W} {\mathrm{cm}}^{-2}.$(Round off to the Nearest Integer), (Assume complete absorption and normal incidence conditions are there)

Seawater at a frequency $f=9\times {10}^2 \mathrm{Hz}$, has permittivity $\epsilon =80{\epsilon }_0$ and resistivity $\rho =0.25 \mathrm{\Omega } \mathrm{m}$. Imagine a parallel plate capacitor is immersed in seawater and is driven by an alternating voltage source $V\left(t\right)=V_0\sin \left(2\pi ft\right)$. Then the conduction current density becomes ${10}^{\mathrm{x}}$ times the displacement current density after time $t=\frac{1}{800} \mathrm{s}.$ The value of $x$ is _______

(Given $\left.:\frac{1}{4\pi {\epsilon }_0}=9\times {10}^9 \mathrm{N} {\mathrm{m}}^2 {\mathrm{C}}^{-2}\right)$