Question

A plane electromagnetic wave travels in vacuum along z-direction. What can you say about the directions of its electric and magnetic field vectors? If the frequency of the wave is 30 MHz, what is its wavelength?

Answer 1

The electromagnetic wave travels in a vacuum along the z-direction. The electric field (E) and the magnetic field (H) are in the x-y plane. They are mutually perpendicular. 
Frequency of the wave, \(ν = 30 \  MHz\) =\( 30 \times  10^6 s^{−1 }\)
Speed of light in a vacuum, \(c = 3 \times  10^8 \ m/s\) 
Wavelength of a wave is given as:

\(λ = \frac cv\)

\(λ = \frac {3 \times  10^8}{30 \times 10^6}\)

\(λ = 10\  m\)