(See related pages)
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| Index of refraction | the ratio of the velocity of light in vacuum to that through another medium of interest. (See page(s) 822; Sec. 14.3) |
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| Absorptivity | the fraction of the incident light that is absorbed by a material. (See page(s) 822; Sec. 14.4) |
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| Luminescence | absorption of light or other energy by a material and the subsequent emission of light of longer wavelength. (See page(s) 822; Sec. 14.5) |
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| Fluorescence | absorption of light or other energy by a material and the subsequent emission of light within 10-8 s of excitation. (See page(s) 822; Sec. 14.5) |
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| Phosphorescence | absorption of light by a phosphor and its subsequent emission at times longer than 10-8 s. (See page(s) 822; Sec. 14.5) |
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| Laser | acronym for light amplification by stimulated emission of radiation. (See page(s) 822; Sec. 14.6) |
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| Laser beam | a beam of monochromatic, coherent optical radiation generated by the stimulated emission of photons. (See page(s) 822; Sec. 14.6) |
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| Population inversion | condition in which more atoms exist in a higher-energy state than in a lower one. This condition is necessary for laser action. (See page(s) 822; Sec. 14.6) |
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| Optical communication | a method of transmitting information by the use of light. (See page(s) 822; Sec. 14.7) |
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| Light attenuation | decrease in intensity of the light. (See page(s) 822; Sec. 14.7) |
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| Optical waveguide | a thin-clad fiber along which light can propagate by total internal reflection and refraction. (See page(s) 822; Sec. 14.7) |
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| Superconducting state | a solid in the superconducting state that shows no electrical resistance. (See page(s) 822; Sec. 14.8) |
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| Critical temperature | the temperature below which a solid shows no electrical resistance. (See page(s) 822; Sec. 14.8) |
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| Critical current density | the current density above which superconductivity disappears. (See page(s) 822; Sec. 14.8) |
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| Critical field Hc | the magnetic field above which superconductivity disappears. (See page(s) 822; Sec. 14.8) |
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| Meissner effect | the expulsion of the magnetic field by a superconductor. (See page(s) 822; Sec. 14.8) |
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| Type I superconductor | one that exhibits complete magnetic-flux repulsion between the normal and superconducting states. (See page(s) 822; Sec. 14.8) |
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| Type II superconductor | one in which the magnetic flux gradually penetrates between the normal and superconducting states. |
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| Lower critical field | the field at which magnetic flux first penetrates a type II superconductor. (See page(s) 823; Sec. 14.8) |
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| Upper critical field | the field at which superconductivity disappears for a type II superconductor. (See page(s) 823; Sec. 14.8) |
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| Fluxoid | a microscopic region surrounded by circulating supercurrents in a type II superconductor at fields between Hc2 and Hc1. (See page(s) 823; Sec. 14.8) |