The number of spectral lines in a hydrogen atom is . . . . . . .

$A$ hydrogen atom is excited from the ground state to a state with principal quantum number $n = 4$. The number of spectral lines emitted in the emission spectrum is:

The ratio of the maximum wavelengths of the Lyman and Balmer series in the hydrogen spectrum is ........

In the Lyman series,the series limit of wavelength is $\lambda_1$. The wavelength of the first line of the Lyman series is $\lambda_2$ and in the Balmer series,the series limit of wavelength is $\lambda_3$. Then the relation between $\lambda_1$,$\lambda_2$,and $\lambda_3$ is

In a hydrogen atom,when an electron transitions from the fourth orbit to the ground state,find the wavelength of the emitted photon in $nm$.

The first wavelength of the Paschen series in hydrogen is $18,800 \, \mathring A$. What is the minimum wavelength of the Paschen series in $\mathring A$?