Uniform plan waves satisfy the following conditions:
1. At every point in space E and H are perpendicular to each other and to the direction of propagation. No fields, therefore, in the direction of wave propagation.
2. Everywhere in space, the fields vary harmonically with time and at the same frequency.
3. Each field has the same direction, magnitude and phase at every point in any plane perpendicular to the direction of wave propagation. The fields, therefore, are only function of the coordinate that represents the direction of wave propagation.