Which of the following is incorrect about a plane electromagnetic wave?

$A$ point light source emits electromagnetic ($E$.$M$.) waves in free space. $A$ detector, placed at a distance of $L \text{ m}$, measures the intensity as $I_o$. The detector is now shifted to another location on the same spherical surface, ensuring the angle between the original location and the new location is $45^{\circ}$. The measured intensity at the new location will be . . . . . . .

The speed of electromagnetic waves in a medium is $1.5 \times 10^8 \ m/s$. If the relative permittivity of that medium is $2$,then its magnetic susceptibility is (speed of light in vacuum is $3 \times 10^8 \ m/s$).

The vectors $\vec{E}$ and $\vec{B}$ of an electromagnetic wave in vacuum are

For a plane electromagnetic wave, the electric field is given by $\overrightarrow{E} = 90 \sin (0.5 \times 10^{3} x + 1.5 \times 10^{11} t) \hat{k} \text{ V/m}$. The corresponding magnetic field $\vec{B}$ will be

The oscillating electric and magnetic vectors of an electromagnetic wave are oriented along