Question

the filament of a light bulb is cylindrical with length l = 20 mm and radius r = 0.05 mm. the filament is maintained at a temperature T = 5000 K by an electric current. the filament behaves approximately as a black body, emitting radiation isotropically. at night, you observe the light bulb from a distance D = 10 km with the pupil of your eye fully dilated to a radius r = 3 mm.

what is the total power radiated by the filament?

how much radiation power enters your eye?

Answer 1