Threshold wavelength of a metal is 4000 ~A ^ . It light of wavelength 3000 Å irradiates the surface, the maximum kinetic energy of photoelectron is

Step-by-step solution

If the maximum kinetic energy of photoelectron emitted from the surface of a metal is E_K and W is the work function of the metal, the from Einstein's photoelectric equation we have E_K=h v-W where, h v is the energy of the photon absorbed by the electron in the metal. Also v= c = velocity wavelength =E_K= h c - h c ₀ =h c ( 1 - 1 ₀ ) Given, aligned & =3 10⁻⁷ ~m ₀ & =4 10⁻⁷ ~m . aligned aligned E_K=6.6 10⁻³⁴ & 3 10^8 & ( 1 3 10⁻⁷ - 1 4 10⁻⁷ ) J aligned = 19.8 10⁻¹⁹ 12 1.6 10⁻¹⁹ eV =1.03 1 eV