Given that, 2eV≤ϕ≤5eV
Wavelength corresponding to minimum and maximum values of work function are
λmax=hcE=4×10−15×3×1032=6×10−7m=600nm
And λmin=hcE=4×10−15×3×1085=2.4×10−7m=240nm
Clearly, wavelength range would be: 240≤λ≤600
Thus, wavelength 650 nm is not suitable for photoelectric effect.