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Materials that allow the transmission of light waves through them are called optically transparent. Chemically pure (undoped) window glass and clean river or spring water are prime examples of this. Materials that do not allow the transmission of any light wave frequencies are called opaque. Such substances may have a chemical composition which ...
An opaque substance transmits no light, and therefore reflects, scatters, or absorbs all of it. Other categories of visual appearance, related to the perception of regular or diffuse reflection and transmission of light, have been organized under the concept of cesia in an order system with three variables, including opacity, transparency and ...
Metallic and insulating states of materials can be considered as different quantum phases of matter connected by a metal-insulator transition. Materials can be classified by the structure of their Fermi surface and zero-temperature dc conductivity as follows: [4] Metal: Fermi liquid: a metal with well-defined quasiparticle states at the Fermi ...
Materials that inhibit the passage of electromagnetic radiation are called radiodense or radiopaque, while those that allow radiation to pass more freely are referred to as radiolucent. Radiopaque volumes of material have white appearance on radiographs, compared with the relatively darker appearance of radiolucent volumes. For example, on ...
There are also weaker dependencies on temperature, pressure/stress, etc., as well on precise material compositions (presence of dopants, etc.); for many materials and typical conditions, however, these variations are at the percent level or less. Thus, it's especially important to cite the source for an index measurement if precision is required.
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Optical materials are transparent materials from which optical lenses, prisms, windows, waveguides, and second-surface mirrors can be made. They are required in most optical instruments . Most optical materials are rigid solids , but flexible and elastic materials are used for special functions.
A basic distinction is between isotropic materials, which exhibit the same properties regardless of the direction of the light, and anisotropic ones, which exhibit different properties when light passes through them in different directions. The optical properties of matter can lead to a variety of interesting optical phenomena.