Question

The work function of a metal is $1.6\times {10}^{-19}J.$ When the metal surface is illuminated by the light of wavelength 6400 Å, then the maximum kinetic energy of emitted photo-electrons will be
(Planck's constant h = $6.4\times {10}^{-34}Js)$

• A. $14\times {10}^{-19}J.$
• B. $2.8\times {10}^{-19}J.$
• C. $1.4\times {10}^{-19}J.$
• D. $1.4\times {10}^{-19}eV.$

Answer 1

The correct option is C $1.4\times {10}^{-19}J.$

$K_{max}=\frac{hc}{\lambda }-W_0=\frac{6.4\times {10}^{-34}\times 3\times {10}^8}{6400\times {10}^{-10}}-1.6\times {10}^{-19}=1.4\times {10}^{-19}J$