The energy required to ionise a hydrogen like ion in its ground state is 9 Rydbergs. What is the wavelength of the radiation emitted when the electron in this ion jumps from the second excited stale to the ground state?

Step-by-step solution

h c λ = 13 . 6 e V z 2 1 n 1 2 - 1 n 2 2 n 1 = 1 n 2 = 3 h c λ = 13.6 e V 3 2 1 1 2 - 1 3 2 ⇒ h c λ = 13.6 e V 9 8 9 Wavelength = 1240 8 × 13.6   nm λ = 11.39  nm