Answer
277 nm, ultraviolet.
Work Step by Step
The minimum photon energy is the energy of the covalent bond, 4.48 eV.
$$E= hf=h\frac{c}{\lambda} $$
$$\lambda =\frac{hc}{E}=\frac{1.24\times10^{-6}eV\cdot m}{4.48eV}=277nm$$
You can help us out by revising, improving and updating this answer.
Update this answerAfter you claim an answer you’ll have 24 hours to send in a draft. An editor will review the submission and either publish your submission or provide feedback.