$A$ hydrogen atom is excited from the ground state to another state with a principal quantum number equal to $4$. The number of spectral lines in the emission spectra will be:

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

In the Balmer series,the wavelength of the first line is $\lambda_1$ and in the Brackett series,the wavelength of the first line is $\lambda_2$. Then,the ratio $\frac{\lambda_1}{\lambda_2}$ is:

If $917 \mathring A$ is the lowest wavelength of the Lyman series,then the lowest wavelength of the Balmer series will be .......$\mathring A$.

What is the shortest wavelength present in the Paschen series of spectral lines (in $;nm$)?

The wavelength of the Lyman series is given by which of the following expressions?