What is the photon flux (photons/ m2 s) at a distance of 1 km from a light source emitting 50W of radiation in the visible domain, with wavelength 6000 Angstroms.
The Attempt at a Solution
Energy of one photon = hc/λ = 3.32 x 10-19J.
So, number of photons per second = 50/3.32 x 10-19 = 1.51 x 10-20.
So, photon flux = 1.51 x 10-20/4π(1000)2 = 1.20 x 1013.
Is this correct?