Physics - Heat & Thermo Question with Solution | TestHub

The filament of a light bulb has surface area $64{\text{ mm}}^2$. The filament can be considered as a black body at temperature $2500K$ 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 $=5.67\times 10^{-8}{\text{Wm}}^{-2}{\text{ K}}^{-4}$, Wien's displacement constant $=2.90\times 10^{-3}m-K$, Planck's constant = $6.63\times 10^{-34}\text{ Js}$, speed of light in vacuum = $3.00\times 10^8{\text{ ms}}^{-1}$ )