Electromagnetic Waves

The energy in a cubic centimeter of space due to an electromagnetic wave can be shown² to be

where K and μ, are the dielectric constant and the magnetic permeability, respectively, of the transmitting medium (each unity for free space), and E and H are the electric and magnetic intensities of the wave.

The velocity of propagation of an electromagnetic wave in any medium can be shown² to be

where c, the velocity of light in free space, has the value 3 X 10¹⁰, and μ and K are as given in the preceding paragraph. In free space (approximately so for air), μ and K are both unity, and thus the velocity of an electromagnetic wave is 3*10¹⁰ centimeters per second.

An electromagnetic wave has a direction of polarization,¹ which is the direction of the electric component or electric field. The discussions that follow will be limited to vertically polarized waves and horizontally polarized waves.