Question

The work function for the surface of aluminium is 4.2 eV. What potential difference will be required to stop the most energetic electrons emitted by light of wavelength 2000 Å? What should be the wavelength of the incident light for which the stopping potential is zero?

Answer 1

Data: Φ = 4.2eV, λ₁ = 2 × 10^-7 m,V₀₂ = 0,

h = 6.63 × 10^-34 J∙s, c = 3 × 10⁸ m/s, 

e = 1.6 × 10^-19 C

(i) In the first case, the stopping potential is

(ii) In the second case,