The absorption spectra of ions have been used to identify the presence of the elements in the atmospheres of the Sun and other stars. (In fact, the element helium was discovered in the spectrum of the Sun before it was identified on Earth, hence its name.) What is the wavelength of light (in nm) that is absorbed by He⁺ ions when they are excited from the Bohr orbit with n = 3 to the n = 4 state?