What do electromagnetic waves $NOT$ transport?

An electromagnetic wave of frequency $\nu = 3.0\,MHz$ passes from vacuum into a dielectric medium with permittivity $\varepsilon = 4.0\varepsilon_0$. Then

To radiate $EM$ signal of wavelength $\lambda$ with high efficiency,the antennas should have a minimum size equal to

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

An electromagnetic wave has its electric and magnetic fields given by $\vec{E}(t) = \vec{E}_m \sin(kx - \omega t)$ and $\vec{B}(t) = \vec{B}_m \sin(kx - \omega t)$. If the directions of $\vec{E}_m$ and $\vec{B}_m$ are in the direction of $\hat{i} + \hat{j}$ and $\hat{i} - \hat{j}$ respectively,the unit vector that gives the direction of propagation of the wave is:

About $20 \%$ of the power of a $100 \ W$ bulb is converted to visible radiation. Assuming that the radiation is emitted isotropically and neglecting reflection,the average intensity of visible radiation at a distance of $5 \ m$ is $\frac{\alpha}{25 \pi} \ W/m^2$. The value of $\alpha$ is