The equation for the energy of the electron in the hydrogen atom is given in your text(s) as E= - 2.18 x 10^-18J x (1/n_f^2 - 1/n_i^2). However the actual equation is -2.18 x 10^-18j x Z^2(1/n_f^2 - 1/n_i^2) where Z= nuclear charge (number of protons in the nucleus). It is important to note that this equation only works for single electron species. With this equation in mind, answer the following question.
Without calculation, predict which transition will produce light of longer wavelength
(1) a transition from n = 4 to n = 1 in the hydrogen atom or (2) a transition from n = 4 to n =2 in the He^+ ion.