Question

The work function of sodium metal is 4.41 × 10^–19 J. If photons of wavelength 300 nm are incident on the metal, the kinetics energy of the ejected electrons will be (h = 6.63 × 10^–34Js; c = 3 × 10⁸ m/s) ______× 10^–21 J.

Numerical Value Type

Answer 1

Ans. 222

Sol.

Metal (Work function = E₀)

E = E₀ + (kE)_max

${hC\over\lambda}=4.41×10^{–19}+kE$

${6.63×10^{-34}×3×108\over300×10^{-9}}= 4.41×10^{-19}+kE$

So, (kE)_max = 6.63 × 10^–19 – 4.41 × 10^–19

= 2.22 × 10^–19

= 222 × 10^–21J