= Lumen
{disambiguate=unit}
{title2=$\mathrm{lm}=\mathrm{cd\,sr}$}
{wiki}
= Lumen
{synonym}
The <lumen> is the <International System of Units> unit of <luminous flux>: $1\,\mathrm{lm}=1\,\mathrm{cd}\,\mathrm{sr}$. A source with constant <luminous intensity> $1\,\mathrm{cd}$ within a cone of <solid angle> $1\,\mathrm{sr}$ supplies $1\,\mathrm{lm}$ into that cone. A source with the same <luminous intensity> in every direction supplies $4\pi\,\mathrm{lm}$ over a full <sphere>. <SI base unit: candela (cd)>{ref}
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