The work function of a metal is 3 eV. Which colour of visible light can cause photoelectric emission from the metal?
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Question

The work function of a metal is 3 eV. Which colour of visible light can cause photoelectric emission from the metal?

G1 Physics · Accepted Answer

The threshold photon energy must be at least equal to the work function: E = φ = 3 eV. Using E(eV) = 1240/λ(nm), the threshold wavelength is λ₀ = 1240/3 ≈ 413 nm. Photoelectric emission requires λ ≤ 413 nm. Among the listed visible colours, blue light has sufficiently short wavelength to satisfy this condition. Correct option: B.