The filament of a light bulb has a surface area 64 mm The

Last updated: 6/9/2023

The filament of a light bulb has a surface area 64 mm The filament can be considered as a black body at temperature 2500 K emitting radiation like a point source when viewed from far At night the light bulb is observed from a distance of 100 m Assume the pupil of the eyes of the observer to be circular with radius 3 mm Then Take Stefan Boltzmann constant 5 67 x 10 8 Wm 2K 4 Wien s displacement constant 2 90 10 m K Planck s constant 6 63 10 34 Js speed of light in vacuum 3 00 x108 ms a power radiated by the filament is in the range 642 W to 645 W b radiated power entering into one eye of the observer is in the range 3 15 10 8 W to 3 25 x 10 8 W c the wavelength corresponding to the maximum intensity of light is 1160 nm d taking the average wavelength of emitted radiation to be 1740 nm the total number of photons entering per second into one eye of the observer is in the range 375 x 1011 to 3 85 x 1011