Question

The work function of tungsten is $4.50eV$. Calculate the speed of fastest electron ejected from tungsten surface when light whose photon energy is $5.80eV$ shines on the surface.

Answer 1

Given that $W=4.5eV$ and $E=5.8eV$

so Maximum kinetic energy possible will be

$KE=E-W=5.8eV4.5eV=1.3eV=1.3\times 1.6\times {10}^{-19}Joule$

and $KE=\frac{m{v}^2}{2}$ .......(1)

so putting value of $m=9.1\times {10}^{-31}Kg$ in equation-1

we get $v=6.76\times {10}^{5}m/s$