A large family of waves, each with a different wavelength range is called the electromagnetic spectrum (sometimes shortened to the EM spectrum). These waves all travel at the speed of light (300,000,000 metres per second) in a vacuum.
The table below lists the different radiations in the electromagnetic spectrum and shows some information about each radiation.
|Type of wave||Typical source||Example of detector||Approximate wavelength||Typical users||Dangers of over exposure|
|Radio: LW||electronic circuits, stars and space||aerial and electronic circuit||1km||communications, radio, TV||safe (unless very concentrated)|
|Radio: MW||electronic circuits, stars and space||aerial and electronic circuit||100m||communications, radio, TV||safe (unless very concentrated)|
|Radio: VHF||electronic circuits, stars and space||aerial and electronic circuit||1m||communications, radio, TV||safe (unless very concentrated)|
|Microwaves||electronic circuits, cool objects||aerial and electronic circuit||1cm (10-2m)||communications satellites, telephony, heating water and food||burning, if concentrated|
|Infra red (IR)||electronic devices, warm objects, sun||electronic detectors, special photographic film, blackened thermometer||0.1mm (10-4m)||magic eyes in security lighting, remote control (eg TV)||burning, if concentrated|
|Light; Red, Orange, Yellow, Green, Blue, Indigo, Violet||electronic devices (LED), hot objects, sun||eye, photographic film, electronic devices (eg, LDR)||0.001mm (10-6m)||seeing, photography, worldwide communication using optical fibres||burning, blindness if concentrated|
|Ultraviolet (UV)||gas discharge, very hot objects, UV lamps, sun||photographic film||0.00001mm (10-8m)||sun-tan lamp, making ions, making vitamin D, water purification plants to kill bacteria||sunburn, skin cancer|
|X-rays||very fast electrons hitting a metal target||photographic film||10-10m||imaging defects in bones, hidden devices||cell destruction, cell mutation, cancer|
|Gamma rays ( )||radioactive nuclei decaying||photographic film, GM tube||10-12m||medical tracers, killing cancerous cells, sterilisation||cell destruction, cell mutation, cancer|