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Electromagnetic spectrum - Wikipedia, the free encyclopedia |
 | | The electromagnetic spectrum, shown in the table, extends from frequencies used in the electric power grid (at the long-wavelength end) to gamma radiation (at the short-wavelength end), covering wavelengths from thousands of kilometres down to fractions of the size of an atom. |
| | At the other extreme, photons of arbitrarily high frequency may be produced by colliding electrons with positrons at appropriate energy. |
| | Use of the radio frequency spectrum is regulated by governments. |
| en.wikipedia.org /wiki/Electromagnetic_spectrum (1439 words) |
