The work function for the following metals is given $Na: 2.75 \; ev,k=2.30 \;ev ,Mo:4.17\;ev,Ni:5.15\;ev$ which of these metal will not give photo electric emission for a radiation of wave length , $3300 A^{\circ}$ from a He - cd laser placed 1 m away from the photo cell ?

Question

$\begin{array}{1 1} \text{Emission will occur in all the metals } \\ \text{Emission will occur in Mo and Ni} \\ \text{Emission will occur in Na and k } \\ \text{Emission will occur only in Na } \end{array}$