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坎德拉

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坎德拉(英语即拉丁语candela)又称烛光,是发光强度的单位,国际单位制七个基本单位之一,符号 cd

1979年10月第十六届国际计量大会将坎德拉定义为:给定一个频率为540.0154×1012 Hz的单色辐射光源(黄绿色可见光),该辐射源在某个方向的辐射强度英语Radiant intensity为1/683瓦特球面度,则该辐射源在该方向的发光强度为1坎德拉[1]。1坎德拉的点状光源所发出的总光通量为4π流明。一支普通蜡烛的发光强度约为1cd。

早期人们曾把每1白炽灯的发光强度称之为一支烛光,例如25瓦的就称之为25支烛光。其原因是一只100W的白炽灯发出的光通量约等于400π流明,换算后每1W的发光强度约为1cd。

与通常测量辐射强度或测量能量强度的单位相比较,发光强度的定义考虑人的视觉因素和光学特点,是在人的视觉基础上建立起来的。

参考资料

  1. ^ Unit of luminous intensity (candela). The NIST Reference on Constants, Units, and Uncertainty. [2013-11-24]. (原始内容存档于2013-12-16). 
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坎德拉
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