Optics/Light

From Wikibooks, the open-content textbooks collection

Light is generally understood to be a visible form of electromagnetic radiation. Visible light has a range of wavelengths that are visible to the eye. The range of wavelengths of visible light waves are from around 400nM (nanometres) for blue light, to about 700nM for red. However, the entire spectrum of light is much more broad than just the visible form. The entire spectrum includes the infrared and ultraviolet wavelengths, both of which are invisible to our eyes, yet they are still considered "light". Light may be classified simultaneously (depending on the experiment), as both a wave and a stream of particles, called photons.