In a photoelectric experiment, the emitter plate is irradiated with radiation of \(200\ \text{nm}\). The photocurrent becomes zero when the collector plate potential is \(-0.80\ \text{V}\). Calculate the work function (in eV) of the emitter.
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For photoelectric effect problems, remember the two important formulas:
\[
E_{\text{photon}}=\frac{1240}{\lambda(\text{nm})}\ \text{eV}
\]
and
\[
h\nu=\phi+eV_0.
\]
A quick method is:
\[
\boxed{\phi=\frac{1240}{\lambda(\text{nm})}-V_0}
\]
when all quantities are expressed in electron volts and volts.