please help me with these 3 questions

8. When UV light at 58.4nm from a helium lamp is directed upon a sample of krypton, electrons are ejected with a speed of 1.79106m/s. Calculate the ionization potential of krypton. 9. The work function for metallic caesium is 2.24eV. Calculate the kinetic energy and speed of electrons ejected if a light source of a) 250nm and b) 600nm is used. 0 . Describe one experiment, that shows the particle character of photons. Give one technologic application of this principle