Question

When UV light of wavelength 285 nm falls on a metal surface, themaximum kinetic energy of emitted electrons is 1.40 eV. What is thework function of the metal?
eV

Answer 1

photoelectric effect equation:

    E = φ + E_kmax
    hc/λ = φ + E_kmax
   
    φ = hc/λ - E_kmax
    = 4.1357x10^-15eVs x2.99792458x10⁸ms^-1 / 285x10^-9m -1.40eV
        = 2.95eV

Answer 2

When light falls on metal surface. Electrons are ejected from the surface of metal, if the energy of light falling on it higher than a certain wavelength. The minimum energy of the light which ejects electrons from the surface is called work function of the metal. The maximum kinetic energy of electrons ejected from the metal is the difference between the energy of light falling on it and the work function of the metal. Therefore Rearrange for W. hc C-(1.40 eV) (6.626 x 10-34 Js)(3x108 m/s)( (285x10- m) 1eV ev-(1.40 eV) 1.6x10 J - 2.959 eV Therefore, the work function of the metal is 2.96 eV