$${\lambda= \frac{hc}{E}=\frac{6,63 \cdot 10^{-34} \times 3 \cdot 10^8}{10^4 \times 1,6 \cdot 10^{-19}}=1,24 \cdot 10^{-10}\, \mathrm{m}=0,12\, \mathrm{nm}}$$