Given :-
Wavelength of incident UV light, lamda = 2000 A⁰ = 2000 x 10^-10m
Work function of the material, W₀ = 5 eV = 5 x 1.6 x 10^-19J

We know that, h (frequency) = W₀ + K.E._max
i.e., h (frequency) = W₀ + e Vs
i.e., e Vs = h (frequency) - W₀
i.e., Vs = [h (frequency)] / e - W₀ / e
i.e., Vs = [h c] / [(lamda) e] - W₀ / e
i.e., Vs = [(6.6 x 10^-34J.s) (3 x 10⁸m/s)] / [( 2000 x 10^-10m) (1.6 x 10^-19C)] - (5 x 1.6 x 10^-19J) / (1.6 x 10^-19C)
i.e., Vs = (6.19 - 5) = 1.19 Volts.

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By :-   Dr. A. W. Pangantiwar