Diffraction of microwaves and radio waves. Illustration showing a communications mast and radio transmitter transmitting microwave signals (shorter wavelength, grey) and radio waves (longer wavelength, red). Microwaves are used in communications such as mobile phone systems. Radio waves are used for radio and TV signals. A large hill presents an obstacle between the transmitter and the house receiving the signals. The longer wavelength radio waves spread out more as a result of diffraction by the hill, and radio reception at the house is good. The shorter wavelength microwaves are diffracted less, so mobile phone reception is poor, the signal being obscured by the hill.