To stop the fastest photoelectrons emitted by nickel (work function 5.01 eV) under ultraviolet light of wavelength 200 nm, the required retarding potential is:
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Question

To stop the fastest photoelectrons emitted by nickel (work function 5.01 eV) under ultraviolet light of wavelength 200 nm, the required retarding potential is:

G1 Physics · Accepted Answer

Photon energy E = hc/λ = (1240 eV·nm)/(200 nm) = 6.20 eV. Kₘₐₓ = 6.20 − 5.01 = 1.19 eV. Hence stopping-potential magnitude is 1.19 V ≈ 1.2 V; the polarity to stop electrons is retarding. Source answer: D (1.2 V).