Microwaves are shown to be located above frequencies used for the television transmission and below those in the infrared and some used for radar detection, with frequencies detected by our eyes occupying a narrow band between infra red and ultra violet. Note that the energy of the waves increases with frequency.
Microwaves form part of the Industrial, Scientific and Medical bands (ISM) originally set aside for non-communications purposes. i.e. used for microwave heating equipment medical diathermy units and scientific research etc. While there are a number of frequencies available for microwave cooking, in the UK and worldwide, 2.45GHz is generally used as the frequency for domestic cooking. In recent years this unlicensed band has seen the introduction of communications systems including “Bluetooth”, cordless and mobile phones, WiFi and RFID systems etc.
The particular choice of frequency and the its’ usage is dependent upon regulations within individual countries and regions.