The threshold wave length ,for photo electric emission from a material is $5200 A^{\circ}$ photo electron will be emitted when this material is illuminated with monochromatic radiation from a

Question

$\begin{array}{1 1} \text{50 watt infra red lamp } \\ \text{1 watt infra red lamp } \\ \text{50 watt ultra violet lamp } \\ \text{1 watt ultra violet lamp } \end{array} $