Question

Electrons are emitted with zero velocity from a metal surface when it is exposed to radiation of wavelength 6800 Å. Calculate threshold frequency ($v_{0}$) and work function ($W_{0}$) of the metal.

NCERT Class XII
Chemistry - Main Course Book I

Chapter 2. Structure of Atom

Answer 1

W₀ = work function of the metal is given by the minimum energy required to eject an electron from the surface of a metal, by excitation with photons - light.

W₀ is the energy in photons in the light, which is just enough to emit an electron with a zero kinetic energy

   f₀ = threshold frequency

 W₀ = h f₀ = h c / λ₀  = 6.626 * 10⁻³⁴  * 3 * 10⁸ / 6800 * 10⁻¹°   Joules
            W₀   = 2.923 * 10⁻¹⁹ Joules
=> work function W₀  = 1.827 eV