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SI radiometry unitsQuantity Symbol SI unit Abbr. Notes

Radiant energy Q joule J energy

Radiant flux watt Wradiant energy per unit time, also called radiant power

Radiant intensity I watt/steradian W.sr-1 power per unit solid angle

Radiance Lwatt/steradian/square meter

W.sr-

1.m-2

power per unit solid angle per unit projected source area called intensity in some other fields of study

Irradiance E, I watt/square meter W.m-2power incident on a surface, sometimes confusingly called intensity

Radiant exitance / Radiant emittance

M watt/square meter W.m-2 power emitted from a surface

Radiosity J or Jλ watt/square meter W.m-2 emitted plus reflected power leaving a surface

Spectral radianceLλ

orLv

watt/steradian/meter3

orwatt/steradian/square meter/hertz

W.sr-

1.m.-3

orW.sr-

1.m-2.Hz-

1

commonly measured in W.sr-1.m-

2.nm-1

Spectral irradiance

Eλ

orEv

watt/meter3

orwatt/square meter/hertz

W.m-3

orW.m-

2.Hz-1

commonly measured in W.m-2.nm-1

SI photometry unitsQuantity Symbol SI unit Abbr. Notes

Luminous energy Qv lumen second lm.s units are sometimes called talbotsLuminous flux F lumen (= cd.sr) lm also called luminous powerLuminous intensity

Iv candela (=lumen/sr) cd an SI base unit

Luminance Lv candela/square meter cd/m2 units are sometimes called "nits"Illuminance Ev lux (= lm/m2) lx used for light incident on a surfaceLuminous Mv lux (= lm/m2) lx used for light emitted on a surface

emittanceLuminous efficacy

lumen/watt lm/Wratio of luminouos flux to radiant flux

Sumber Cahaya

Radiasi panas (radiasi benda hitam) o bola lampu o matahari o partikel padat bercahaya dalam suhu tinggi(lihat api)

emisi spektral atomik o laser dan masero light emitting diode o lampu gas(lampu neon, lampu air raksa lamps dsb)o api dari gas

percepatan dari partikal bebas bermuatan(biasanya sebuah elektron) o radiasi siklotron o Radiasi Bremsstrahlungo Radiasi Cherenkov

kemoluminesens floresens fosforescence

o tabung sinar katoda bioluminesens sonoluminesens triboluminesens peluruhan radioaktif anihilasi partikel-antipartikel