If hydrogen gas is enclosed in a sealed tube and heat to high temperatures, it emits radiation. If this radiation is passed through a prsim, components are different wavelengths get deviated by different amounts and we get the hydrogen spectra on a screen. In the spectra of hydrogen atom, it is observed that light of wavelength 656.3 nm and then light of wave length 486.1 nm are present. Hydrogen atoms do not emit any radiation between 656.3 nm and 486.1 nm. Similarly radiation is observed at 434.1 nm and 4202.nm.
In the invisible region also, there is radiation emitted by the hydrogen atom at discrete wavelengths.
The wavelengths nicely fit the equation
1/λ = R [1/n² - 1/m²]
where R = 1.09737*10^7 m-1.
n and m are integers with m>n.
The spectrum in the ultraviolet region is called Lyman series and you get the series by setting n = 1.
The hydrogen spectrum in the visible region is called Balmer series and you get the series by setting n = 2.
The hydrogen spectrum in infrared region is called Paschen series and you get the series by setting n= 3.