Editing Optical coating (section)

====Extreme ultraviolet coatings====
In the [[ultraviolet|EUV]] portion of the spectrum (wavelengths shorter than about 30&nbsp;nm) nearly all materials absorb strongly, making it difficult to focus or otherwise manipulate light in this wavelength range.  Telescopes such as [[TRACE]] or [[Extreme ultraviolet Imaging Telescope|EIT]] that form images with EUV light use multilayer mirrors that are constructed of hundreds of alternating layers of a high-mass metal such as [[molybdenum]] or [[tungsten]], and a low-mass spacer such as [[silicon]], [[vacuum deposition|vacuum deposited]] onto a substrate such as [[glass]].  Each layer pair is designed to have a thickness equal to half the wavelength of light to be reflected.  [[Constructive interference]] between scattered light from each layer causes the mirror to reflect EUV light of the desired wavelength as would a normal metal mirror in visible light.  Using multilayer optics it is possible to reflect up to 70% of incident EUV light (at a particular wavelength chosen when the mirror is constructed).