The absorption spectra of ions have been used to identify the presence of the elements in the atmospheres of the sun and other stars. What is the wavelength of light (in nm) that is absorbed by He+ ions, when an electron is excited from the Bohr orbit with n = 2 to the n = 5 state? The energy of an electron in the nth level is

E(subcript n) = -(BZ^2/n^2)

where B = 2.18 x 10-18 J and Z = charge on nucleus (number of protons).