What is the wavelength of light emitted when the electron in a hydrogen atom undergoes transition from an energy level with n = 4 to an energy level with n = 2?

Question 2.13: What is the wavelength of light emitted when the electron in a hydrogen atom undergoes transition from an energy level with n = 4 to an energy level with n = 2?

Answer
The n_i = 4 to n_f = 2 transition will give rise to a spectral line of the Balmer series. The energy involved in the transition is given by the relation,

E = - (4.0875 × 10^-19 J)

The negative sign indicates the energy of emission.
Wavelength of light emitted


Substituting the values in the given expression of λ: