The work function of a metal is 4.0ev. If the metal is irradiated with radiation of wavelength 300nm,then the maximum K.E  of the photoelectrons would be about

Given, λ=300nm =300×10-9m           E=hCλ=6.6×10-34×3×1083×10-7=6.6×10-19J Work function,W=4ev=4×1.6×10-19=6.4×10-19J According to photoelectric effect, E=W+K.E   K.E=6.6×10-19-6.4×10-19=0.2×10-19J=2×10-20J