The only electron in the hydrogen atom resides under ordinary conditions in the first orbit. When energy is supplied, the electron moves to higher energy orbit depending on the amount of energy obsorbed. When this electron returns to any of the lower orbits, it emits energy. Lyman series is formed when the electron return to the lowest orbit while Balmer series is formed when the electron returns to second orbit. Similarly, Paschen , Brackett and Pfund series are formed when eletron returns to the third, fourth and fifth orbits from higher energy orbits respectively.