Radiation of wavelength λ is incident on a photocell and the fastest emitted electron has speed v. If the wavelength is changed to 3λ/4, how does the fastest-electron speed change?
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Radiation of wavelength λ is incident on a photocell and the fastest emitted electron has speed v. If the wavelength is changed to 3λ/4, how does the fastest-electron speed change?

G1 Physics · Accepted Answer

Einstein equation gives K₁=hc/λ−φ and K₂=4hc/(3λ)−φ. Since K₂ = K₁ + hc/(3λ) and K₁<hc/λ, K₂ > (4/3)K₁. Therefore v₂/v = √(K₂/K₁) > √(4/3). Correct answer: B.