A Calcium surface (work function = 2.87 eV) is illuminated with 200 nm light from a 2 mW laser.
How many photons per second are emitted by the laser?
Only a small fraction of these photons can interact with electrons at the surface. Suppose this fractional efficiency is 0.018%.
What is the current in the detector assuming all the emitted electrons are captured?
Note that current is charge(in Coulombs) per second. The charge of one electron is 1.6 x 1019C