Light of wavelength λ is incident on three photoelectric cells having threshold wavelengths λ₁, λ₂ and λ₃. The stopping potentials are V₁, V₂ and V₃. Given λ₁ < λ, λ₂ > λ and λ₃ ≫ λ, which relation is correct?
Options

Question

Light of wavelength λ is incident on three photoelectric cells having threshold wavelengths λ₁, λ₂ and λ₃. The stopping potentials are V₁, V₂ and V₃. Given λ₁ < λ, λ₂ > λ and λ₃ ≫ λ, which relation is correct?

Options

G1 Physics · Accepted Answer

Step 1: Photoemission occurs only when incident wavelength λ ≤ threshold wavelength λ₀. Step 2: Cell 1 has λ₁ < λ, so incident photons do not reach the threshold energy; hence no photoelectrons and V₁ = 0 in the question's convention. Step 3: Cells 2 and 3 emit electrons. Their maximum electron kinetic energies satisfy eVₛ = hc(1/λ − 1/λ₀). Step 4: Since λ₃ ≫ λ₂ > λ, the term 1/λ₃ is smaller; thus V₃ > V₂. Final answer: V₁ = 0 and V₂ < V₃ (Option A).