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The candela ( or ; symbol: cd) is the SI base unit of luminous intensity; that is, luminous power per unit solid angle emitted by a point light source in a particular direction. Luminous intensity is analogous to radiant intensity, but instead of simply adding up the contributions of every wavelength of light in the source's spectrum, the contribution of each wavelength is weighted by the standard luminosity function (a model of the sensitivity of the human eye to different wavelengths).〔 A common candle emits light with a luminous intensity of roughly one candela. If emission in some directions is blocked by an opaque barrier, the emission would still be approximately one candela in the directions that are not obscured. The word ''candela'' means ''candle'' in Latin. ==Definition== Like most other SI base units, the candela has an operational definition—it is defined by a description of a physical process that will produce one candela of luminous intensity. Since the 16th General Conference on Weights and Measures (CGPM) in 1979, the candela has been defined as:〔(【引用サイトリンク】 work = The NIST Reference on Constants, Units, and Uncertainty )〕
The definition describes how to produce a light source that (by definition) emits one candela. Such a source could then be used to calibrate instruments designed to measure luminous intensity. The candela is sometimes still called by the old name ''candle'',〔(Merriam-Webster )〕 such as in ''foot-candle'' and the modern definition of ''candlepower''. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「candela」の詳細全文を読む スポンサード リンク
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