Question

Electrons are emitted with zero velocity from a metal surface when it is exposed to radiation of wavelength 6800 Å. Calculate threshold frequency (V₀) and work function (W₀) of the metal.

Answer 1

Wavelength of the radiation, λ = 6800 Å = 6800 x 10^-10 m

Work function of the metal, W₀ = hv₀ = hc/λ

= {6.626 x 10^-34 Js x 3 x 10⁸ ms^-1}/{6800 x 10^-10 m}

= 2.91 x 10^-19 J

and threshold frequency, v₀ = W₀/h = {2.92 x 10^-19 J}/{6.626 x 10^-34 Js} = 4.41 x 10¹⁴ s^-1

or, v₀ = 4.41 x 10¹⁴ Hz