The electromagnetic spectrum is a continuum of all electromagnetic waves arranged according to frequency and wavelength. The sun, earth, and other bodies radiate electromagnetic energy of varying wavelengths. The electromagnetic spectrum is familiar in day to day life. The microwave ovens and cell phones emit and receive energy that is part of the Electromagnetic Spectrum. The light that human eyes can see is also part of the electromagnetic spectrum. This visible part of the electromagnetic spectrum consists of the colors that are seen in a rainbow - from reds and oranges, through blues and purples. Infrared light lies between the visible and microwave portions of the electromagnetic spectrum. Infrared light has a range of wavelengths, just like visible light has wavelengths that range from red light to violet. "Near infrared" light is closest in wavelength to visible light and is what is used as the energy source in proximity sensing applications.