...are commonly used for communication, tracking systems. Although there are several bounderies used by different people, up to today the use of radiowaves is limited to around 300GHz. Although the use can be quite different, radio waves overlap microwaves. Some mobile phone frequencies are at the same time used in a microwave-oven ! Luckely for us, at extremely low intensety.
Stars, Sun, gases in space, communication, tracking systems, ..
This band of the spectrum is most crowded with uses for 1001 applications such as:
Communication: Submarine, Marine, Aerial, Telegraphy, CB, Phone, Mobile phones, satellite, radar, TV, radio, Space
Interaction with matter: