If a photo cell is illuminated with a radiation of $1240 \;A^{\circ}$, the stopping potential is found to be $6V$ , then the work function of the emitter and the threshold wavelength are

Question

$\begin{array}{1 1} 2eV,6200 A^{\circ} \\ 3eV,3140 A^{\circ} \\4eV,3100 A^{\circ}\\ 6eV,2070 A^{\circ}\end{array} $