Missing lines in a continuous spectrum reveal

In hydrogen spectrum,which of the following spectral series lies in the ultraviolet region?

The difference between the frequencies of the second and first Paschen lines of the hydrogen atom is (where $R$ is the Rydberg constant and $c$ is the speed of light in vacuum).

The ionization energy of the electron in the hydrogen atom in its ground state is $13.6 \text{ eV}$. The atoms are excited to higher energy levels to emit radiations of $6$ wavelengths. The maximum wavelength of the emitted radiation corresponds to the transition between:

Find the ratio of the wavelength of the first line of the Lyman series for a doubly ionized lithium atom $(Li^{2+})$ to the wavelength of the first line of the Lyman series for deuterium $(D)$.

The frequencies for the series limit of the Balmer and Paschen series are $f_1$ and $f_3$,respectively. If the frequency of the first line of the Balmer series is $f_2$,then the relation between $f_1, f_2$,and $f_3$ is: