Q.
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 state to the ground state ?
En=−n2 Ionisation energy =n2−qR
now, when it jumps, the released energy will be
E2−E1=−qR(91−1)=8R Now, E=λhc=8Rλ=8Rhc=8×2.2×10−186.64×10−34×3×108=11.31nm≈11.4nm