The electromagnetic (EM) spectrum

Electromagnetic waves form a spectrum of different wavelengths. This spectrum includes visible light, X-rays and radio waves. Electromagnetic radiation can be useful as well as hazardous.

The electromagnetic spectrum

The electromagnetic spectrum is a continuous range of wavelengths. The types of radiation that occur in different parts of the spectrum have different uses and dangers - depending on their wavelength and frequency.

Refraction from a prism
Refraction from a prism

The order of electromagnetic waves in the spectrum is shown in the table.

EnergyFrequencyWavelengthRadiation typeTypical use
LowestLowestLongestRadio wavesTelevision signals
MicrowavesCooking, mobile phones
InfraredOptical fibre communication
Visible lightSeeing
UltravioletDetecting forged bank notes
X-raysMedical images of bones
HighestHighestShortestGamma radiationKilling cancer cells

Radio waves have the lowest frequencies and longest wavelengths, while gamma waves have the highest frequencies and shortest wavelengths.

All of these waves travel at the same speed in free space, which is the speed of light or about 300,000,000 m/s (metres per second).