Changes

'''Light''' can refer to [[electomagnetic]] [[radiation]] of any [[wavelength]], or to EM radiation of visible wavelengths <ref>Wavelengths of EM spectrum <i>usbyte.com</i> [http://www.usbyte.com/common/approximate_wavelength.htm]</ref> ; that stimulate the [[organ]]s of sight, having for normal human vision wavelengths ranging from about 3900 to 7700 [[ångstrom]]s (390 to 780 [[nm]]), violet has the shortest wavelength and red has the largest.

'''Light''' can refer to [[electromagnetic]] [[radiation]] of any [[wavelength]], or to EM radiation of visible wavelengths <ref>Wavelengths of EM spectrum <i>usbyte.com</i> [http://www.usbyte.com/common/approximate_wavelength.htm]</ref> ; that stimulate the [[organ]]s of sight, having for normal human vision wavelengths ranging from about 3900 to 7700 [[ångstrom]]s (390 to 780 [[nm]]), violet has the shortest wavelength and red has the largest.

It travels at the [[speed of light]]: about 186,300 [[mile]]s (300,000 kilometres) per second.  

It travels at the [[speed of light]]: about 186,300 [[mile]]s (300,000 kilometres) per second.