Color and Wavelength
Light is an electromagnetic wave. Visible light has wavelengths from about 400 nm (400 x 10-9 m) for violet light through about 700 nm (700 x 10-9 m) for red light. Our eyes are most sensitive to light in the middle of this range, such as yellow light with a wavelength of about 550 nm (550 x 10-9 m). One nanometer (nm) is one-billioneth of a meter, 1 nm = 1 x 10-9 m.
Electromagnetic radiation with longer wavelengths is called infra-red radiation and is often referred to simply as IR radiation. Our eyes can not detect this IR radiation but our skin feels it as heat. Electromagnetic radiation with wavelengths shorter than the visible range is called ultra-violet radiation and is often shortened to UV radiation. Again, our eyes can not detect this UV radiation but its effects are real. UV radiation causes sunburns and suntans; UV radiation can also cause skin cancer and eye damage. Electromagnetic radiation is often abbreviated and people will talk of EM radiation or EM waves.
(C) 2003, Doug Davis; all rights reserved