The work function of a metal is 4.0 eV. If the metal is irradiated with radiation of wavelength 200 nm, then the maximum kinetic energy of the photoelectrons would be about

W0=4.0 eV=hcλ0             =4 × 1.6 × 10−19  J              = 6.4  ×  10−19  J given   λ  =  200  nm=200×  10−9 m=2×10-7m      E = hC  λ=6.625×10-34×3×1082×10-7m=9.9×10-19Now  apply   E=W + K.EK.E =E-W =9.9×10-19- 6.4  ×  10−19  J=3.5×10-19J