The electric field in an electromagnetic wave is given as $\vec{E}=20 \sin \omega\left(t-\frac{x}{c}\right) \vec{j} NC ^{-1}$ Where $\omega$ and $c$ are angular frequency and velocity of electromagnetic wave respectively. The energy contained in a volume of $5 \times 10^{-4}\, m ^3$ will be $.....\times 10^{-13}\,J$

(Given $\varepsilon_0=8.85 \times 10^{-12}\,C ^2 / Nm ^2$ )

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

If ${\varepsilon _0}$ and ${\mu _0}$ are respectively, the electric permittivity and the magnetic permeability of free space. $\varepsilon $ and $\mu $ the corresponding quantities in a medium, the refractive index of the medium is

The electric field of plane electromagnetic wave of amplitude $2\,V/m$ varies with time, propagating along $z-$ axis. The average energy density of magnetic field (in $J/m^3$ ) is

The electric field associated with an em wave in vacuum is given by $\vec{E}=\hat{i} 40 \cos \left(k z-6 \times 10^{8} t\right)$ where $E, x$ and $t$ are in $volt/m,$ meter and seconds respectively. The value of wave vector $k$ is....$ m^{-1}$

A red $LED$ emits light at $0.1$ watt uniformly around it. The amplitude of the electric field of the light at a distance of $1\ m$ from the diode is....$ Vm^{-1}$