In the second semester of this course we shall show that the
electric and magnetic field obey a wave equation of the form.
and hence that a there is a possibility for a propagating
electromagnetic disturbance in our Universe. In this expression
and 
are the vacuum permeability and permitivity which can be measured independently through
experiments that do not involve electromagnetic waves. From the wave equation we derive the velocity of electromagnetic waves
The speed of light! Such electromagnetic waves are truly
omnipresent in nature corresponding to radio-waves, infrared radiation, light, x-rays, and gamma-rays all of which are solutions
to Eq. 23 and travel with the same velocity, c.