Question

Electrons are emitted with zero velocity from a metal surface when it is exposed to radiation of wavelength 6800 Å. Calculate threshold frequency ( $v_0$ ) and work function ( $W_0$ ) of the metal.

Answer 1

Threshold wavelength of radiation $\left({\lambda }_0\right)=6800A=6800\times {10}^{-10}m$
Threshold frequency $\left(v_0\right)$ of the metal
$\frac{c}{{\lambda }_0}=\frac{3\times {10}^{8}m{s}^{-1}}{6.8\times {10}^{-7}m}=4.41\times {10}^{14}{s}^{-1}$
Thus, the threshold frequency $\left(v_0\right)$ of the metal is 4.41 × ${10}^{14}{s}^{–1}$.
Hence, work function ($W_0$ ) of the metal = h${\nu }_0$
= (6.626 × ${10}^{–34}$ Js) (4.41 × ${10}^{14}{s}^{–1}$ )
= 2.922 × ${10}^{–19}$ J