Electromagnetic Spectrum

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Maxwell's Theory predicts the existence of electromagnetic radiation at essentially any wavelength or frequency. For obvious reasons, the mysteries of light were first explored in the optical region to which our eyes respond, but this represents only a minute fraction of the spectral regions that have been opened over the years. Electronic oscillators can generate electromagnetic waves with very long wavelengths. Lasers, hot filaments, light-emitting diodes (LEDs), and many other sources can generate light in the optical regime. X-rays are generated by electron collisions at medium energies, and the shortest wavelengths, ; (gamma) rays, are generated by high-energy nuclear collisions and in radioactive decay. The wave shown here in red is not to scale: The frequency of electromagnetic waves changes by over twenty orders of magnitude from the radio portion of the spectrum to gamma rays. (Unit: 5)