Values of work function ( W_0) for a few metals are given below The number of metals which will show photoelectric effect when light of wavelength…

Values of work function $\displaystyle \left(\mathrm{W}_0\right)$ for a few metals are given below

Metal	Li	Na	K	Mg	Cu	Ag
$\displaystyle \mathrm{W}_{\mathrm{o}} / \mathrm{eV}$	$\displaystyle 2.42$	$\displaystyle 2.3$	$\displaystyle 2.25$	$\displaystyle 3.7$	$\displaystyle 4.8$	$\displaystyle 4.3$

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