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adelinetohyj adelinetohyj
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9 years ago
A 100 W light bulb is 20% efficient (i.e. 80% of its output is invisible infra-red
radiation and only 20% is visible light). A person can see the light with the naked
eye from a distance of 10 km on a dark night. If the area of the pupil of the persons
eye is 0.50 cm2, what power of the visible light is received by the eye of the person?
(A) 2.4×10−16 W
(B) 8.0×10−13 W
(C) 1.5×10−12 W
(D) 2.0×10−9 W
(E) 8.0×10−9 W
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#1
Educator
9 years ago
Quote from: adelinetohyj (9 years ago)
(B) 8.0×10−13 W
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