In a hydrogen atom, electron moves from second excited state to first excited state and then from the first excited state to the ground state. Find the ratio of the wavelengths obtained.

Find the relation between the three wavelengths ${\mathrm{\lambda }}_1,{\mathrm{\lambda }}_2$ and ${\lambda }_3$ from the energy level diagram shown in the Fig. 20.19.

The ionisation energy of a hydrogen-like Bohr atom is $4$ rydbergs.

What is the wavelength of radiation emitted when the electron jumps from first excited state to ground state?

The ionisation energy of a hydrogen-like Bohr atom is $4$ Rydbergs.

What is the radius of the first orbit for this atom? Given that Bohr radius of hydrogen atom $=5\times {10}^{-11} \mathrm{m}$ and $1$ Rydberg $=2.2\times {10}^{-18} \mathrm{J}$

A doubly ionised lithium atom is hydrogen-like with atomic number $3$. How many spectral lines are observed in the emission spectrum of the above exciting system?