Microwaves

Microwaves were the first EM waves in this spectrum to be discovered experimentally, by Hertz in 1888, and they are produced by oscillator electric circuits containing a capacitor and an inductor, or by special vacuum tubes such as the klystron tube designed for higher-frequency operation.

Two properties stand out: microwaves heat certain substances on which they are incident (the basis of microwave cooking), and they can be detected using crystal detectors. Their practical uses reflect both of these properties and their relatively short wavelength: transmission of TV signals, long-distance telephone communication, cooking in microwave ovens, radar systems used to locate distant objects such as ships and aeroplanes (their short wavelength allows a narrow, directional beam and good spatia …