Hydrogen atoms are excited from ground state to the state of principal quantum number $4$. Then,the number of spectral lines observed will be . . . . . . .

The wavelength of radiation emitted is ${\lambda _0}$ when an electron jumps from the third to the second orbit of a hydrogen atom. For the electron jump from the fourth to the second orbit of the hydrogen atom,the wavelength of radiation emitted will be

In the hydrogen spectrum,the shortest wavelengths of the Lyman and Balmer series are $\lambda_1$ and $\lambda_2$ respectively. The Rydberg constant of hydrogen is

If $\lambda_{1}$ and $\lambda_{2}$ are the wavelengths of the third member of the Lyman series and the first member of the Paschen series respectively,then the value of $\lambda_{1} : \lambda_{2}$ is

If radiation of all wavelengths from ultraviolet to infrared is passed through hydrogen gas at room temperature,absorption lines will be observed in the:

Let $\lambda_P$ and $\lambda_L$ be the longest wavelengths observed in the Paschen and Lyman series respectively. Choose the correct option.