The number of metals which will show photoelectric effect when light of wavelength 400 nm falls on it is ____.
Given:
$$
\begin{aligned}
& \mathrm{h}=6.6 \times 10^{-34} \mathrm{~J} \mathrm{~s} \\
& \mathrm{c}=3 \times 10^8 \mathrm{~m} \mathrm{~s}^{-1} \\
& \mathrm{c}=1.6 \times 10^{-19} \mathrm{C}
\end{aligned}
$$