Photon flux from a light source

  • #1
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Homework Statement



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.

Homework Equations



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?
 

Answers and Replies

  • #2
35,442
11,877
1.51*10-20 photons per second? I think that is a typo.

The approach is good, and the numbers look reasonable.
 
  • #3
1,344
33
1.51*10-20 photons per second? I think that is a typo.

Yeah! That is a typo!

The approach is good, and the numbers look reasonable.

Thanks!
 

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