Lumen (unité)

Lumen
Informations
Système Unités dérivées du Système international
Unité de… Flux lumineux
Symbole lm
Conversions
1 lm en... est égal à...
  Unités SI   1 cd sr

Le lumen (du latin, lumière) est l’unité dérivée du Système international du flux lumineux ; son symbole est lm[1].

Définition

Par définition, 1 lumen correspond au flux lumineux émis dans un angle solide de 1 stéradian (sr) par une source lumineuse isotrope (ponctuelle uniforme) située au sommet de l’angle solide et dont l’intensité lumineuse vaut 1 candela (cd)[2].

lm = 1 cd sr.

Le lumen est une unité photométrique, tout comme la candela dont elle est dérivée, elle est fondée sur la perception humaine de la lumière à l'aide de la fonction d'efficacité lumineuse spectrale.

Selon la définition de la candela, pour une efficacité lumineuse relative spectrale maximale, c'est-à-dire de 100 % (pour une onde monochromatique de fréquence 540 × 1012 Hz et donc de longueur d'onde 555 nm dans le vide) : 1 lm = 1/683 W.

Voir aussi

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Liens externes

Notes et références

  1. Informations lexicographiques et étymologiques de « Lumen » dans le Trésor de la langue française informatisé, sur le site du Centre national de ressources textuelles et lexicales.
  2. Élie Lévy, Dictionnaire de physique, Presses universitaires de France, Paris, 1988, p. 486.

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