_:b19779 . . "\u03A6_v" . _:b19778 _:b19779 . . _:b19778 . . . . _:b19792 . . . _:b19778 . . "\u03A6" . . . "Illuminance is the total luminous flux incident on a surface per unit area."@en . "illumination"@en . . . _:b19779 . . . _:b19779 . _:b19778 . _:b19792 . _:b19792 . . . . _:b19792 . . . . "illuminance"@en . . .