When a metal was exposed to photons at a frequency of 1.18×10^15 s−1, electrons were emitted with a maximum kinetic energy of 3.70×10^−19 J.

Question

Calculate the work function, Φ, of this metal. Φ =J/photon

What is the maximum number of electrons that could be ejected from this metal by a burst of photons (at some other frequency) with a total energy of 5.22×10−7 J?

Answer 1

Hi Bri L.,

So calculate the total energy/photon per E = h ν . You should get units of J!

The observed maximum kinetic energy represents what's left over after the work function is subtracted from the incident photon energy, so plug in the values you have now. The work function, multiplied by the maximum possible number of electrons generated, will equal the total energy given. Note that that is the maximum possible, if the incident energy were expended at 100% efficiency of ejection, by photons of just sufficient energy to eject with negligible kinetic energy. But such efficiency is not seen under that condition.

A related consideration is the efficiency of photon generation by thermally heated surfaces. You might want to look up what Coleman lanterns use in their mantles, and why?

-- Cheers, -- Mr. d.