= Solution
The incident <photon energy> is
$$
E_\gamma=\frac{hc}{\lambda}=\frac{1239.841984\,\mathrm{eV\,nm}}{456\,\mathrm{nm}}=2.71895\,\mathrm{eV}.
$$
Subtracting the <work function> gives $K_{\max}=0.768952\,\mathrm{eV}=1.2320\times10^{-19}\,\mathrm J$. This is much less than the electron rest <energy>, so nonrelativistic <kinetic energy> is adequate:
$$
\boxed{v_{\max}=\sqrt{\frac{2K_{\max}}{m_e}}\simeq5.20\times10^5\,\mathrm{m\,s^{-1}}.}
$$
The magnitude of the retarding <stopping potential> satisfies $eV_s=K_{\max}$, so
$$
\boxed{V_s\simeq0.769\,\mathrm V.}
$$
The collector must be negative relative to the emitting surface to retard the <electrons>; the quoted number is the magnitude. Contact-potential corrections are neglected.
Back to article page
