Calculating photons per second (1 Viewer)

[rand_althor]

I was looking at the in2Physics@HSC textbook and saw this example question. Can someone please explain how they get the formula for number of photons per second for b.?

 

[InteGrand]

I was looking at the in2Physics@HSC textbook and saw this example question. Can someone please explain how they get the formula for number of photons per second for b.?

Power = energy/time (by definition) = energy/photons × photons/time = (energy per photon)×(photons per second).

∴ photons per second = Power/(energy per photon).

It's basically the chain rule.

 

[rand_althor]

Oh okay that makes sense. Thanks for the help!