OpenStax College Physics for AP® Courses, Chapter 29, Problem 34 (Problems & Exercises)

This is College Physics Answers with Shaun Dychko. We are going to figure out how many x-ray photons are created when a single x-ray photon has an energy of 75.0 kiloelectron volts and the total output has a power of 1.00 watt. So the power is the number of photons times the energy per photon divided by time and we want to know what is this N per t factor what is this number per time or photons per second in other words? And we will solve for it by dividing both sides by the energy per photon and so the number per time is the power divided by the energy per photon. So that's 1.00 joule per second, which I have written instead of watts just because it helps understand where this per second comes from in this equation so the seconds are the unit in the denominator of this part here. So we have 1.00 joule per second divided by 75.0 times 10 to the 3 electron volts per photon and then convert that into joules by multiplying by 1.602 times 10 to the minus 19 joules per electron volt and we end up with photons per second in our final units here and that is 8.32 times 10 to the 13 photons per second.