| (1) $\dfrac{1}{6}\times10^5$ | (2) $\dfrac{1}{6}\times10^6$ | (3) $\dfrac{5}{7}\times10^4$ | (4) $\dfrac{5}{7}\times10^5$ |
\textbf{172.} In a photoelectric experiment, the threshold frequency of the metal is $\frac{5}{4}\times10^{15}$ Hz. If the energy of each photon incident on the metal is $4.125\times10^{-19}$ J, how many photoelectrons are produced per meter per second?
$$\left(h = 4\times10^{-15}\ \text{eV·s},\quad m_e = 9\times10^{-31}\ \text{kg},\quad c = 1.6\times10^{-19}\ \text{C}\right)$$
\begin{tabular}{llll}
(1) $\dfrac{1}{6}\times10^5$ & (2) $\dfrac{1}{6}\times10^6$ & (3) $\dfrac{5}{7}\times10^4$ & (4) $\dfrac{5}{7}\times10^5$
\end{tabular}
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