Microwave radiation is a form of electromagnetic radiation that has a frequency of between 0.3 and 300 gigahertz, which places it between radio and infrared waves on the electromagnetic spectrum. The corresponding wavelengths of microwaves are between 1 millimeter and 1 meter. The term "radiation" in this case refers to the radiation and movement of electromagnetic waves rather than to radioactivity.
The most common use of microwaves is in microwave ovens used to heat food. However, the spectrum of electromagnetic waves that count as microwaves is so broad that they have been split into different bands that are used for different things. The waves used in microwave ovens are called the S band and range between 2 and 4 GHz in frequency. This band is also used by Bluetooth, cell phones and GPS.
High frequency microwaves between 90 and 140 GHz are called the F band and are used for radio astronomy and modern radar. Those between 110 and 170 GHz are called the D band and are used for amateur radio, millimeter wave scanning and microwave remote sensing.
Scientific studies have not shown a connection between microwave radiation and cancer, but exposure to high levels of microwaves from a broken microwave oven can cause deep tissue burns. For this reason, microwave ovens should never be operated when they do not close properly.