Consider an electron in a hydrogen atom occupying the third energy level and another electron in an ionized helium atom occupying the second energy level. In the Bohr model, what is the ratio of their orbital radii, $\backslash (\backslash$frac$\{$r$(\backslash$mathrm$\{$H$\})\}\{$r$(\backslash$mathrm$\{$He$\})\}\backslash )?$

$3/4$

$9$

$9/2$

$3/2$

$9/4$