A photoelectric experiment is performed on a clean potassium surface.
a. (i) Define the term threshold frequency ν0 for a metal.
b. (ii) The intensity of incident light is gradually increased while its frequency is kept fixed at 0.8ν0. Explain, with reason, whether photoelectrons will be emitted in this situation.
c. (iii) Keeping the frequency again fixed at 0.8ν0, the temperature of the potassium surface is raised by 50∘C. State, with proper justification, whether the rise in temperature can trigger photoelectric emission.