Values of work function \(\left({\mathrm{W}}_{0}\right)\) for a few metals are given below: \begin{equation} \begin{arra…

Values of work function \(\left({\mathrm{W}}_{0}\right)\) for a few metals are given below:

\begin{equation}
\begin{array}{|c|c|c|c|c|c|c|}
\hline \text { Metal } & \mathrm{Li} & \mathrm{Na} & \mathrm{K} & \mathrm{Mg} & \mathrm{Cu} & \mathrm{Ag} \\
\hline \mathrm{W}_0 / \mathrm{eV} & 2.42 & 2.3 & 2.25 & 3.7 & 4.8 & 4.3 \\
\hline
\end{array}
\end{equation}

The number of metals which will show photoelectric effect when light of wavelength \(400\mathrm{nm}\) falls on it is_________

Given: \(\mathrm{h}=6.6\times {10}^{-34}\mathrm{J}\mathrm{s}\)

\(c=3\times {10}^{8}{\mathrm{ms}}^{-1};\mathrm{e}=1.6\times {10}^{-19}\mathrm{C}\)