The work function for caesium atom is 1.9 eV. Calculate (a) The threshold wavelength and (b) The threshold frequency of the radiation. If the caesium element is irradiated with a wavelength 500 nm, calculate the kinetic energy and the velocity of the ejected photoelectron.

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Alok Kumar Singh | Contributor-Level 10

9 months ago

W₀ = 1.9 eV = 1.9 x 1.602 x 10^-19 J

Threshold frequency, v₀ = W₀ / h = (1.9 x 1.602 x 10^-19 J) / (6.626 x 10^-34Js)

= 0.459 x 10¹⁵ s^-1 = 4.59 x 10¹⁴ s^-1

Threshold wavelength? ₀ = c / v₀ = (3 x 10⁸ ms^-1) / (4.59 x 10¹⁴ s^-1)

= 0.6536 x 10^-6 m = 653.6 nm? 654 nm

Kinetic energy, E = E₀ + ½ mv²

(1/2 mv²) = E

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