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Question
Q451) The work function of a metal is 4.2eV. If radiations of 2000Ao fall on the metal then the kinetic energy of the fastest photo electron is



SOLUTION

Work function φ=4.2 eV=4.2 × 1.60 ×10-19 J
φ=6.72 ×10-19 J
Energy of radiation

∴ K.E. of electron==(9.94 - 6.72) ×10-19 J
K.E of electron=3.32 ×10-19 J
Answer:(c)