Electromagnetic waves are the waves in which electric and magnetic fields vary with time and space with the same frequency. The variations of electric and magnetic fields are sinusoidal in character and both of them vibrate perpendicular to each other and perpendicular to the direction of propagation of the wave.
Some important points:
(1) Electromagnetic waves can travel through vacuum.
(2) These waves are produced by accelerated or oscillating electric charge.
(3) The sinusoidal variations of and occur with the same frequency and hence they attain the maxima and minima at the same time .
(4) The amplitudes of electric and magnetic fields bear a constant ratio of the speed of light i.e. Eo/Bo = c
(5) The speed of electromagnetic waves is a function of the electric and magnetic properties of the medium in which these waves travel and is independent of the amplitude of the field vectors.
(6) The velocity of light in free space is given by