A hydrogen-like ion has a nucleus of charge $+Z e$ and a single electron outside this nucleus. The energy levels of these ions are $-Z^{2} R_{\mathrm{H}} / n^{2}$ (where $Z=$ atomic number). Calculate the wavelength of the transition from $n=3$ to $n=2$ for $\mathrm{He}^{+}$, a hydrogen-like ion. In what region of the spectrum does this emission occur?