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 $6400\stackrel{\circ }{A}$ , 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

$1.4\times {10}^{-19}J$

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