Question

what is hydrogen spectrum

Answer 1

The spectrum of atomic hydrogen is divided into a number of spectral series, with wavelengths given by the Rydberg formula

Answer 2

hydrogen have only one electron. but there are many orbital for that only one electron. so when hydrogen have the excited state the electron go to the upper orbitals. then when hydrogen come back on the ground state the electron also come back at the ground state orbital. at that time electron release its energy like a light wave. that is the hydrogen spectrum