Atoms And Nuclei

In a mixture of H - He\(^+\) gas (He\(^+\) is singly ionized He atom), H atoms and He\(^+\) ions are excited to their respective first excited states. Subsequently, H atoms transfer their total excitation energy to He\(^+\) ions (by collisions). Assume that the Bohr model of atom is exactly valid.

The wavelength of light emitted in the visible region by He\(^+\) ions after collisions with H atoms is