What is the velocity of electromagnetic waves in conductors?

If $10 \%$ of the power of a $(100 \pi) \ W$ light bulb is converted to visible radiation,then the average intensity of visible radiation at a distance of $10 \ m$ is (in $W \ m^{-2}$)

Which of the following statements are true?
$A.$ Speed of light in vacuum is dependent on the direction of propagation.
$B.$ Speed of light in a medium is independent of the wavelength of light.
$C.$ The speed of light is independent of the motion of the source.
$D.$ The speed of light in a medium is independent of intensity.
Choose the correct answer from the options given below:

$A$ plane electromagnetic wave of wave intensity $6 \ W/m^2$ strikes a small mirror of area $40 \ cm^2$,held perpendicular to the approaching wave. The momentum transferred by the wave to the mirror each second will be:

Which of the following quantities changes when the velocity of light in a vacuum changes?

The ratio of the average electric energy density to the total average energy density of an electromagnetic wave is: