Plz explain in complete detailllll

Dar student,
$$\begin{gathered} Given, \\ {\lambda }_0 =5200 A^o =5200\times {10}^{-10} m =5.7\times {10}^{-7} m \\ and speed = freqency \times wavelength \\ For threshold frequency, {\nu }_0 = \frac{c}{{\lambda }_0} = \frac{3\times {10}^8 }{5.7\times {10}^{-7} }=5.26\times {10}^{15} s^{-1} \\ From electromagnetic spectrum we can observe that the frequency range lies within order of UV rays (8 \times {10}^{14} to 3 \times {10}^{16}) l \\ With high frequency, high power is preferable. \\ hence answer will be option C. 50 watt ultraviolet lamp \end{gathered}$$
as frequency range of infrared lies on300 gigahertz (GHz) up to about 400 terahertz (THz), so the radiation does not belong to infrared lamp. and for 1 watt ultraviolet lamp, the intensity of light is not high enough for photoemission. So, the answer is option C. 50watt UV lamp
Regards,