$A$ certain atomic transition from an excited state to the ground state of the hydrogen atom in one or more steps gives rise to four lines in the ultraviolet region of the spectrum. How many lines does this transition produce in the infrared region of the spectrum?

What is the energy associated with the first orbit of $He^{+}$?

The ratio of the shortest wavelength of two spectral series of the hydrogen spectrum is found to be about $9$. The spectral series are

If the radius of the second Bohr orbit of the $He^{+}$ ion is $105.8 \, pm$, what is the radius of the third Bohr orbit of the $Li^{2+}$ ion?

The deflection of a few $\alpha$-particles when bombarded on a thin gold foil indicates that $.......$

In a mixture of $H$ and $He^{+}$ gases,all $H$ atoms and $He^{+}$ ions are excited to their first excited states. Subsequently,on de-excitation in $H$ atoms,energy is transferred to the excited $He^{+}$ ion. The quantum number $n$ of the $He^{+}$ ion after the energy is transferred is: