It is harder to remove free electrons from copper than from sodium. Which has higher work function.

It is easier to remove an electron from sodium than from copper, why? Which metal has higher value of threshold frequency?

Light from a dicharge tube containing hydrogen atoms falls on the surface of sodium.The kinetic energy of the fastest electrons emitted from sodium is 0.73 eV.The work function for sodium is 1.82 eV. Find the energy of the photons causing the photoelectric emission,

Light from a dicharge tube containing hydrogen atoms falls on the surface of sodium.The kinetic energy of the fastest electrons emitted from sodium is 0.73 eV.The work function for sodium is 1.82 eV.find the quantum numbers of the two levels involved in the emission of these photons,

Light from a dicharge tube containing hydrogen atoms falls on the surface of sodium.The kinetic energy of the fastest electrons emitted from sodium is 0.73 eV.The work function for sodium is 1.82 eV.find the recoil speed of the emitting atom assuming it to be at rest before the transmition.(Ionisation energy of hydrogen is 13.6 eV).

Visible light cannot eject photoelectrons from copper surface, whose work function is 4.4 eV. Why? Prove it mathematically.