SI Units

Lux

Définition

L'unité SI d'éclairement lumineux, mesurant le flux lumineux reçu par unité de surface : un lux équivaut à un lumen par mètre carré (1 lx = 1 lm/m²).

Explication

Direct sunlight delivers about 100,000 lux; an overcast sky provides 1,000 lux; office lighting is typically 300–500 lux; a full moon produces roughly 0.25 lux. The key difference from lumens: lumens measure total light output from a source, while lux measures how much of that light reaches a surface. Moving a lamp twice as far away reduces illuminance by a factor of four (inverse-square law).

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RELATED TERMS

Mètre

L'unité SI de base de longueur, définie comme la distance parcourue par la lumière en 1/299 792 458 de seconde.

Kilogramme

L'unité SI de base de masse, définie par la constante de Planck.

Seconde

L'unité SI de base du temps, définie par les transitions de l'atome de césium-133.

Kelvin

L'unité SI de base de température thermodynamique, dont l'origine est le zéro absolu.

Ampère

L'unité SI de base du courant électrique.