If the radius of the first Bohr orbit is $r$, then the radius of the second Bohr orbit will be

An electron in the $n = 1$ orbit of a hydrogen atom is bound by $13.6\, eV$. The energy required to ionize it is........$ eV$.

The Rydberg constant $R$ for hydrogen is

The number of absorption transitions between the first and the fourth energy states of a hydrogen atom is $3$. The number of emission transitions between these states will be

In a hydrogen atom and a $Li^{2+}$ ion,the electron is in the second excited state. If $l_{H}$ and $l_{Li}$ are the angular momenta of the electrons and $E_H$ and $E_{Li}$ are their respective energies,then:

The ionization potential of a hydrogen-like atom is $122.4 \, V$. Find its atomic number $Z$.