# The work function of sodium metal is 4.41 × 10–19 J. If photons of wavelength 300 nm are incident on the metal,

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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

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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