The electromagnetic waves travel with a velocity

In a plane electromagnetic wave travelling in free space,the electric field component oscillates sinusoidally at a frequency of $2.0 \times 10^{10} \text{ Hz}$ and amplitude $48 \text{ V m}^{-1}$. Then the amplitude of the oscillating magnetic field is: (Speed of light in free space $= 3 \times 10^8 \text{ m s}^{-1}$)

In an electromagnetic wave in free space,the root mean square value of the electric field is $E_{rms} = 6 \, V m^{-1}$. The peak value of the magnetic field is:

In a plane electromagnetic wave,$U_E$ and $U_B$ are the average energy densities of the electric field and magnetic field,respectively. Then,which of the following is the correct option?

The electromagnetic waves travel in a medium at a speed of $2.0 \times 10^{8} \ m/s$. The relative permeability of the medium is $1.0$. The relative permittivity of the medium will be (in $.25$)

The velocity of radio waves in free space is $3 \times 10^{8} \ m/s$. If the wavelength of the radio waves is $150 \ m$,what is their frequency?