electromagnetic radiation

Electromagnetic radiation (EM radiation or EMR or just radiation) is radiation such as light, radio waves, etc. (Much of the dangerous radiation associated with radioactivity is not EMR: much EMR is ubiquitous and harmless in everyday life.) EMR is termed "electromagnetic" because modeling of the nature of electric fields and magnetic fields showed that changes in either produce the other, which can happen such that changes back and forth can propagate as waves, and such waves were deliberately produced by manipulating electric and magnetic fields, producing what we call radio waves. Both in theory and in experiment, these waves showed properties like those of light (such as the same speed, i.e., c), exactly as if light and radio waves are the same thing, except for their frequency. Overall classifications within the electromagnetic spectrum (based on wavelength/frequency ranges):

• gamma rays (GR) (shortest wavelength, with highest frequencies)
• X-rays
• ultraviolet (UV)
• visible light
• infrared (IR)
• radio (longest wavelengths, with lowest frequencies)

For more detail, see electromagnetic spectrum and the Wavelengths Table.