Solving a problem in physics section 21 paragraph 100 q

Solving a problem in physics section 21 paragraph 100 q

100. Electric lamp 100 watt emits 3% of the energy in the form of visible light (λ = 550 nm) uniformly in all directions. How many photons of visible light falls into the pupil of the observer 1c (pupil diameter of 4 mm) at a distance of 10 km from the lamp?

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Detailed solution. Decorated in Microsoft Word 2003. (Target decided to use formula editor)