The graph in the figure shows stopping potential V₀ as a function of the frequency ν of incident radiation for three photosensitive metals X₁, X₂ and X₃. Their threshold frequencies increase in the order X₁, X₂, X₃. If all three metals are illuminated with radiation of the same wavelength whose frequency is above all three thresholds, which metal emits photoelectrons with the greatest maximum kinetic energy?

Question

G1 Physics · Accepted Answer

Einstein's photoelectric equation is Kₘₐₓ = hν-φ. Also, φ = hν₀, where ν₀ is the threshold frequency. For the same incident wavelength, the incident frequency ν is the same for all three metals. Therefore the metal with the smallest work function, equivalently the smallest threshold frequency, gives the largest Kₘₐₓ. From the graph, X₁ has the smallest threshold frequency. Hence X₁ gives the greatest maximum kinetic energy. Correct option: A.