The threshold frequency for a metallic surface corresponds to energy of $6.2\: eV$ and the stopping potential for a radiation incident on this surface is $5V$. The incident radiation lies in

Question

$\begin {array} {1 1} (a)\;Ultraviolet \: region & \quad (b)\;Infrared\: region \\ (c)\;Visible\: region & \quad (d)\;X-ray\: region \end {array}$