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## Homework Statement

If the energy flux associated with a light beam of wavelength 3 x10^-7 m is 10 W/m^2, estimate how long it would take, classically, for sufficient energy to arrive at a potassium atom of radius 2 x 10^-10 m in order that an electron be ejected. What would be the average emission rate of photoelectrons if such light fell on a piece of potassium 10^-3 m^2 in area? Would you expect your answer to the latter questions to be significantly affected by quantum mechanical considerations?

## Homework Equations

## The Attempt at a Solution

Ok so I'm guessing we can assume the work function of potassium to be 3 x 10^-19 J (calculated in answer to a previous question)

So thinking about the first question, I'm just not sure how to work it out..

So classically, we imagine photons are arriving at the surface of this potassium atom at 10 W/m^2, so how do i work out energy arriving at the atom per second? Do I work out the surface area of the atom, and assume light is arriving at all directions?