ABSTRACT
We commonly choose frequency or wavelength to distinguish between different forms of electromagnetic energy. In lighting, we generally use wavelength to make a distinction between different types of light. The range of measured wavelengths produced by radiant sources is extreme. At one end of the electromagnetic spectrum we find electrical waves with wavelengths measured in miles. The 60-cycle electrical currents that are used in our homes may have a wavelength of over 3,000 miles. Many other forms of electromagnetic radiation (ER) are associated with wavelengths so small that a special unit, the angstrom (Å), has been introduced to measure them. One angstrom is equal to 1/254,000,000 of an inch. At the opposite end of the electromagnetic spectrum from electricity are cosmic rays, which may have a wavelength as small as 1/10,000 of an angstrom. The electromagnetic spectrum is a collection of different types of radiant energy that can be specified through their varied wavelengths.
