The figure shows the four lowest energy levels of the $\text{He}^{+}$ ion, at $-54.4$, $-13.6$, $-6.04$ and $-3.40\ \text{eV}$, and four downward jumps of its electron, marked P, Q, R and S. Take visible light as wavelengths from $400\ \text{nm}$ to $750\ \text{nm}$. Which jump gives out visible light? Take $hc = 1240.8\ \text{eV nm}$.

Fig. 1: An energy-level diagram of the He+ ion, not to scale. Four horizontal levels are labelled n = 1 at minus 54.4 eV, n = 2 at minus 13.6 eV, n = 3 at minus 6.04 eV and n = 4 at minus 3.40 eV. Four downward arrows show jumps of the electron: P from n = 4 to n = 3, Q from n = 4 to n = 2, R from n = 3 to n = 2, and S from n = 2 to n = 1.