What is threshold frequency in photoelectric emission?

A metal whose work function is 3.3eV is illuminated by light of wavelength 3 xx 10^(-7)m . What is the threshold frequency for photoelectric emission? Plank's constant = 6.6 xx 10^(-34) Js?

What is threshold frequency in the photoelectric effect?

What is photoelectric emission?

Define threshold frequency for photoelectric emission.