When $EM$ wave propagates through vacuum then

A plane electromagnetic wave in a non-magnetic dielectric medium is given by $\vec E\, = \,{\vec E_0}\,(4 \times {10^{ - 7}}\,x - 50t)$ with distance being in meter and time in seconds. The dielectric constant of the medium is

If a source of power $4\ kW$ produces $10^{20}$ photons/second , the radiation belongs to a part of the spectrum called

If electric field intensity of a uniform plane electro magnetic wave is given as

$E =-301.6 \sin ( kz -\omega t ) \hat{a}_{ x }+452.4 \sin ( kz -\omega t )$ $\hat{a}_{y} \frac{V}{m}$

Then, magnetic intensity $H$ of this wave in $Am ^{-1}$ will be

[Given: Speed of light in vacuum $c =3 \times 10^{8} ms ^{-1}$, permeability of vacuum $\mu_{0}=4 \pi \times 10^{-7} NA ^{-2}$ ]

This question has Statement $-1$ and Statement $-2$ . Of the four choices given after the statements, choose the one that best describes the two statements

Statement $-1$ : Sky wave signals are used for long distance radio communication. These signals are in general, less stable than ground wave signals

Statement $-2$ : The state of ionosphere varies from hour to hour, day to day and season to season

Which of the following statement is false for the properties of electromagnetic waves ?