State two properties that are shared by all waves in the electromagnetic spectrum, and for each property, explain why it is significant for the use of electromagnetic waves in communications.

All electromagnetic waves are transverse waves.

Being transverse means the electric and magnetic fields oscillate perpendicular to the direction of propagation, allowing the waves to be polarised. Polarisation can be used to encode information or to reduce interference, which is useful in communication systems.

All electromagnetic waves travel at the same speed of 3.0 × 10⁸ m/s in a vacuum (approximately the same in air).

Because the speed is constant and very high, signals can be transmitted almost instantaneously over long distances, and different parts of the spectrum arrive at the receiver at the same time, simplifying synchronisation and timing in communication networks.