Geometrical OpticsEasy
Question
An illuminance of 2.5 × 105 lm/m2 is produced by sun light falling normally on the surface of the earth. The distance of the earth from the sun is 1.5 × 108 km. The luminious flux of the sun is :-
Options
A.5.6 × 1027 lm
B.7 × 1028 lm
C.7 × 1027 lm
D.5.6 × 1028 lm
Solution
Illuminance I = 
⇒ L = Ir2
Luminious flux of sun φ = 4πL
⇒ L = Ir2Luminious flux of sun φ = 4πL
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