The work function (ϕ) of some metals is listed below. The number of metals which will show photoelectric effect when light of 300 nm wavelength falls on the metal is

The energy associated with incident photon =hcλ⇒E=6.6×10−34×3×108300×10−9JE in eV=6.6×10−34×3×108300×10−9×1.6×10−19=4.16eVSo, number of metals showing photo-electric effects will be (4), i.e., Li, Na, K, Mg